System and method for vehicle fuel system and evaporative emissions system diagnostics

Abstract

The present disclosure provides a system and method for diagnosing a vehicle fuel system and evaporative emissions system. Methods and systems are provided for diagnosing a vehicle fuel system for the presence or absence of undesirable evaporative emissions. In one example, a method includes testing for undesirable evaporative emissions from the fuel system by evacuating the vehicle's fuel system to a variable vacuum level in a first operating mode through an entire fuel vapor canister configured to capture and store fuel vapors, and evacuating the fuel system to the variable vacuum level in a second operating mode through a portion of the fuel vapor canister. In this manner, the diagnosis can be performed in an environmentally friendly manner, wherein analysis of the bleed portion of the test is unaffected by the volatility of the fuel at the time of the diagnosis.

Description

Technical Field

[0001] The present description generally relates to methods and systems for diagnosing the presence or absence of undesirable evaporative emissions from a fuel system and / or evaporative emissions system of a vehicle. Background Art

[0002] A vehicle evaporative emission control system may be configured to store fuel vapors from fuel tank refueling and daytime engine operation, and then purge the stored vapors during subsequent engine operation. For example, the fuel vapors may be stored in a fuel vapor canister. To meet stringent federal emissions regulations, it may be necessary to intermittently diagnose the emission control system for the presence of leaks that could release fuel vapors into the atmosphere.

[0003] A method for testing an emissions control system for the presence of undesirable evaporative emissions may include applying vacuum to an otherwise sealed fuel system and / or evaporative emissions system. If a threshold vacuum is met, this may indicate the absence of severe undesirable evaporative emissions. In some examples, the fuel system may be sealed after the threshold vacuum is reached, and if a pressure loss is less than a loss threshold, or if the rate of pressure loss is less than a loss rate threshold, this may indicate the absence of less severe undesirable evaporative emissions. Failure to meet these criteria may indicate the presence of less severe undesirable evaporative emissions in the fuel system and / or evaporative emissions system. In some examples, intake manifold vacuum may be used as the source of vacuum applied to the emissions control system. However, hybrid-electric vehicles (HEVs) have limited engine run time and, therefore, may have limited opportunities to perform such testing. Furthermore, to improve fuel efficiency, vehicles may be configured to operate at low manifold vacuum and, therefore, may have limited opportunities to perform such testing for undesirable evaporative emissions at sufficient vacuum.

[0004] Therefore, in order to meet emissions regulations, such vehicles may include an onboard vacuum pump, which may be included in an evaporative leak check module (ELCM). The ELCM may be coupled to the evaporative emissions system, for example, within a canister vent line. Thus, the ELCM may supply vacuum for proper leak testing. However, installing an ELCM in a vehicle is a relatively expensive manufacturing cost, which increases with the correlation with the evaporative emissions system and the fuel tank volume. Therefore, it may be desirable to improve the methods for evacuating the fuel system and / or the evaporative emissions system so that costs can be reduced. The inventors herein have recognized these issues.

[0005] Furthermore, there may be situations where pressure bleed testing for the presence or absence of less severe undesirable evaporative emissions may be adversely affected by environmental or vehicle operating conditions. Specifically, bleed may be affected by ambient temperature, fuel temperature, and the like, making interpretation of the results of such testing challenging. For example, if the fuel system is purged to a target of -8 inH₂O, but due to fuel evaporation caused by high ambient temperatures, vacuum is lost by 2-3 inH₂O, the results of such a test may be inconclusive, as interpreting whether the bleed is due to the presence of a source of undesirable evaporative emissions or fuel evaporation is challenging. The inventors herein have recognized these issues.

[0006] Still further, in cases where a vacuum is applied to the fuel system and / or evaporative emissions system while the engine is not in operation, fuel vapors may be drawn into the fuel vapor canister. As fuel vapor is added to the fuel vapor canister, the likelihood of unwanted bleed-through emissions may increase. For example, if the canister is nearly saturated with fuel vapor, any additional fuel vapor may saturate the canister and may cause fuel vapor to escape from the canister to the atmosphere. Therefore, it may be desirable to conduct any testing for the presence or absence of unwanted evaporative emissions in a manner that does not increase the likelihood of bleed-through emissions. The inventors herein have recognized this type of problem. Summary of the Invention

[0007] Therefore, the inventors herein have developed systems and methods to address the aforementioned issues. In one example, a method includes testing for undesirable evaporative emissions from the fuel system by evacuating a vehicle's fuel system to a variable vacuum level in a first operating mode through an entire fuel vapor canister configured to capture and store fuel vapor, and evacuating the fuel system to the variable vacuum level in a second operating mode through a portion of the fuel vapor canister.

[0008] In this way, testing for undesirable evaporative emissions may be performed in an environmentally friendly manner, wherein in some cases the fuel vapor is directed through the canister and in other cases the fuel vapor is directed through only a portion of the canister.

[0009] In one example of the method, the method further includes learning a common route along which the vehicle travels, wherein the learned route includes one or more learned key-off events and further includes expected durations of the one or more learned key-off events, and wherein purging the fuel system in both the first operating mode and the second operating mode is responsive to the learned key-off event duration being below a threshold key-off duration.

[0010] In one example of the method, the variable vacuum level in the first operating mode is a function of the state of charge of the fuel vapor canister and fuel volatility, and the variable vacuum level in the second operating mode is a function of fuel volatility but is independent of the state of charge of the fuel vapor canister. In the first operating mode, purging the fuel system is performed via a vacuum pump positioned between the fuel vapor canister and atmosphere, and in the second operating mode, purging the fuel system is performed via the engine.

[0011] In this way, the fuel system may be evacuated in an environmentally friendly manner, and further in such a manner that the results of the pressure loss portion of the test are not adversely affected by fuel volatility.

[0012] The above advantages and other advantages and features of the present specification will be readily apparent from the following detailed description when considered alone or in conjunction with the accompanying drawings.

[0013] It should be understood that the above summary is provided to introduce a series of concepts in a simplified form, which are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that address any disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A high-level block diagram illustrating an exemplary vehicle system is shown.

[0015] Figure 2 An exemplary vehicle system having a fuel system and an evaporative emissions system is schematically illustrated.

[0016] Figure 3 Systems and methods for determining the presence or absence of undesirable evaporative emissions from a vehicle fuel system based on population data are schematically illustrated.

[0017] Figure 4 A high-level flow chart for determining whether to perform a variable vacuum-based test for undesirable evaporative emissions or a population data-based fuel system diagnostic is depicted.

[0018] Figure 5 Describes a method for predicting the presence or absence of undesirable evaporative emissions. Figure 4 A high-level flow chart of a variable vacuum-based test.

[0019] Figure 6An exemplary lookup table is depicted for determining vacuum values ​​for conducting a variable vacuum based test for the presence or absence of undesirable evaporative emissions.

[0020] Figure 7 A high-level flow chart for testing for undesirable evaporative emissions from a fuel system based on population data is depicted.

[0021] Figure 8 A high-level flow chart illustrating an exemplary method for machine learning common travel routes is shown.

[0022] Figure 9 A high-level flow chart is shown of an exemplary method for scheduling an active variable vacuum evaporative emissions test in response to indicating one or more predicted / learned stops of less than a predetermined duration for a current driving route.

[0023] Figure 10 Shown for Figure 9 High-level flow chart for active variable vacuum evaporative emissions testing.

[0024] Figure 11 An exemplary lookup table is depicted for venting a fuel system to variable vacuum levels while the engine is operating.

[0025] Figure 12 Describes the Figure 5 An exemplary timeline for performing variable vacuum based testing for undesirable evaporative emissions is provided.

[0026] Figure 13 Describes the Figure 7 An exemplary timeline for testing for undesirable evaporative emissions from a fuel system based on population data is provided.

[0027] Figure 14 Describes the Figure 10 An exemplary timeline for conducting active variable vacuum evaporative emissions testing. DETAILED DESCRIPTION

[0028] The following description relates to systems and methods for testing for the presence or absence of undesirable evaporative emissions from a vehicle's fuel system and / or evaporative emissions system. Such methods may be used with hybrid vehicles such as Figure 1 This is particularly relevant to the vehicle system depicted herein, which has limited engine operating time and therefore limited opportunity to purge the fuel vapor storage canister (such as Figure 2 Such methods may include using a vacuum pump to draw variable vacuum levels on the vehicle's fuel system and evaporative emissions system (this is done in Figure 2 ) to perform such diagnostics, where the fuel system includes a steel fuel tank. In some examples, the variable vacuum level may be a function of the fuel vapor canister loading state and the ambient temperature. In scenarios where the conditions for performing diagnostics using the variable vacuum level are not met, a population-based test for the presence or absence of undesirable evaporative emissions may be utilized, such as Figure 3 Place description.

[0029] Figure 4 The general method for selecting whether to perform a variable vacuum test diagnosis or a population-based diagnosis is described in FIG. If the conditions for performing a variable vacuum test diagnosis are met, the patient can be diagnosed based on the Figure 5 Such a method may include evacuating the fuel system to a variable vacuum level via a vacuum pump to perform a pressure loss test for the presence or absence of less severe undesirable evaporative emissions. The variable vacuum level or variable vacuum target may be a function of ambient temperature and canister loading status and may be stored as a 3D lookup table, such as Figure 6 Alternatively, if the conditions for performing a variable vacuum test are not met, the Figure 7 Conduct group-based testing.

[0030] In some examples, the vehicle may be equipped with route learning technology that may enable the vehicle controller to learn routes that the vehicle typically travels, including learned / predicted stops and learned / predicted stop durations. Figure 8 If testing of the fuel system and evaporative emissions system for undesirable evaporative emissions is desired for a particular stop, but the stop has characteristics which may not be possible to perform and complete before the vehicle is turned back on, Figure 5 Variable vacuum diagnostics or Figure 7 The duration of population-based diagnosis can then be determined based on Figure 9 Perform an active variable vacuum test diagnostic. This active variable vacuum test Figure 10, and may include: drawing a variable vacuum level on the fuel system and the evaporative emissions system just prior to a learned / predicted key-off event so that the fuel system and the evaporative emissions system can be sealed at the key-off event to monitor pressure loss to infer the presence or absence of undesirable evaporative emissions. By drawing a variable vacuum on the fuel system and the evaporative emissions system prior to the key-off event, such a pressure loss test can be performed quickly for the duration of the predicted / learned shutdown. While one example of such a test includes using the vacuum pump discussed above, where the variable vacuum is a function of the canister loading state and the ambient temperature, another example may include using the engine intake manifold vacuum to draw a variable vacuum on the fuel system and the evaporative emissions system. In such an example of utilizing the engine intake manifold vacuum for active variable vacuum testing diagnostics, the variable vacuum may be a function of the ambient temperature (and not a function of the canister loading state), as determined by Figure 11 The lookup table shown here is depicted. Figure 12 Describes the use Figures 4 and 5 An exemplary timeline of variable vacuum diagnostics, Figure 13 Describes the use Figure 4 and Figure 7 An exemplary timeline for population-based diagnosis of Figure 14 Describes the Figures 8 to 10 An exemplary timeline for performing active variable vacuum testing for undesirable evaporative emissions is provided herein.

[0031] Figure 1 An exemplary vehicle propulsion system 100 is shown. Vehicle propulsion system 100 includes a fuel-burning engine 110 and a motor 120. As a non-limiting example, engine 110 includes an internal combustion engine, and motor 120 includes an electric motor. Motor 120 can be configured to utilize or consume a different energy source than engine 110. For example, engine 110 can consume liquid fuel (e.g., gasoline) to produce an engine output, while motor 120 can consume electrical energy to produce a motor output. As such, a vehicle having propulsion system 100 can be referred to as a hybrid electric vehicle (HEV).

[0032] Vehicle propulsion system 100 can utilize a variety of different operating modes depending on the operating conditions encountered by the vehicle propulsion system. Some of these modes can enable maintaining engine 110 in a shut-down state (i.e., set to a deactivated state), wherein fuel combustion at the engine is stopped. For example, under selected operating conditions, motor 120 can propel the vehicle via drive wheels 130, as indicated by arrow 122, while engine 110 is deactivated.

[0033] During other operating conditions, engine 110 may be set to a deactivated state (as described above), while motor 120 may be operated to charge energy storage device 150. For example, motor 120 may receive wheel torque from drive wheels 130, as indicated by arrow 122, wherein the motor may convert the vehicle's kinetic energy into electrical energy for storage at energy storage device 150, as indicated by arrow 124. This operation may be referred to as regenerative braking of the vehicle. Thus, in some examples, motor 120 may provide a generator function. However, in other examples, generator 160 may instead receive wheel torque from drive wheels 130, wherein the motor may convert the wheel's kinetic energy into electrical energy for storage at energy storage device 150, as indicated by arrow 162.

[0034] During still other operating conditions, engine 110 can operate by combusting fuel received from fuel system 140, as indicated by arrow 142. For example, engine 110 can be operated to propel the vehicle via drive wheels 130, as indicated by arrow 112, while motor 120 is deactivated. During other operating conditions, both engine 110 and motor 120 can each be operated to propel the vehicle via drive wheels 130, as indicated by arrows 112 and 122, respectively. A configuration in which both an engine and a motor can selectively propel the vehicle can be referred to as a parallel vehicle propulsion system. It should be noted that in some examples, motor 120 can propel the vehicle via a first set of drive wheels, and engine 110 can propel the vehicle via a second set of drive wheels.

[0035] In other examples, vehicle propulsion system 100 can be configured as a series-type vehicle propulsion system, in which the engine does not directly propel the drive wheels. Instead, engine 110 can be operated to provide power to motor 120, which in turn can propel the vehicle via drive wheels 130, as indicated by arrow 122. For example, during selected operating conditions, engine 110 can drive generator 160, as indicated by arrow 116, which can in turn supply electrical energy to one or more of motor 120 (as indicated by arrow 114) or energy storage device 150 (as indicated by arrow 162). As another example, engine 110 can be operated to drive motor 120, which can in turn provide generator functionality to convert engine output into electrical energy, which can be stored at energy storage device 150 for subsequent use by the motor.

[0036] Fuel system 140 may include one or more fuel storage tanks 144 for storing fuel on the vehicle. For example, fuel tank 144 may store one or more liquid fuels, including but not limited to gasoline, diesel, and alcohol fuel. In some examples, fuel may be stored on the vehicle as a mixture of two or more different fuels. For example, fuel tank 144 may be configured to store a mixture of gasoline and ethanol (e.g., E10, E85, etc.) or a mixture of gasoline and methanol (e.g., M10, M85, etc.), wherein these fuels or fuel mixtures may be delivered to engine 110, as indicated by arrow 142. Further other suitable fuels or fuel mixtures may be supplied to engine 110, where they may be burned at the engine to produce engine output. Engine output may be used to propel the vehicle, as indicated by arrow 112, or may be recharged to energy storage device 150 via motor 120 or generator 160.

[0037] In some examples, energy storage device 150 may be configured to store electrical energy that may be supplied to other electrical loads resident on the vehicle (besides the motor), including cabin heating and air conditioning systems, engine starting systems, headlights, cabin audio and video systems, etc. As non-limiting examples, energy storage device 150 may include one or more batteries and / or capacitors.

[0038] Control system 190 may communicate with one or more of engine 110, motor 120, fuel system 140, energy storage device 150, and generator 160. Control system 190 may receive sensory feedback information from one or more of engine 110, motor 120, fuel system 140, energy storage device 150, and generator 160. Control system 190 may send command signals to one or more of engine 110, motor 120, fuel system 140, energy storage device 150, and generator 160 in response to this sensory feedback. Control system 190 may receive an indication of a driver-requested output of the vehicle propulsion system from vehicle driver 102. For example, control system 190 may receive sensory feedback from a pedal position sensor 194 in communication with pedal 192. Pedal 192 may illustratively be a brake pedal and / or an accelerator pedal. Additionally, in some examples, control system 190 can communicate with a remote engine start receiver 195 (or transceiver) that receives a wireless signal 106 from a key fob 104 having a remote start button 105. In other examples (not shown), a remote engine start can be initiated via a cell phone or smartphone-based system where the user's cell phone sends data to a server and the server communicates with the vehicle to start the engine.

[0039] Energy storage device 150 may periodically receive electrical energy from a power source 180 residing external to the vehicle (e.g., not part of the vehicle), as indicated by arrow 184. As a non-limiting example, vehicle propulsion system 100 may be configured as a plug-in hybrid electric vehicle (PHEV), in which electrical energy may be supplied from power source 180 to energy storage device 150 via power transmission cable 182. During operation to recharge energy storage device 150 from power source 180, power transmission cable 182 may electrically couple energy storage device 150 and power source 180. When the vehicle propulsion system is operating to propel the vehicle, power transmission cable 182 may be disconnected between power source 180 and energy storage device 150. Control system 190 may identify and / or control the amount of electrical energy stored at the energy storage device, which may be referred to as the state of charge (SOC).

[0040] In other examples, electrical transmission cable 182 may be omitted, where electrical energy may be wirelessly received from power source 180 at energy storage device 150. For example, energy storage device 150 may receive electrical energy from power source 180 via one or more of electromagnetic induction, radio waves, and electromagnetic resonance. Thus, it should be understood that any suitable means may be used to recharge energy storage device 150 from a power source that is not part of the vehicle. In this manner, motor 120 may propel the vehicle using an energy source other than the fuel used by engine 110.

[0041] Fuel system 140 may periodically receive fuel from a fuel source residing external to the vehicle. As a non-limiting example, vehicle propulsion system 100 may be refueled by receiving fuel via fuel dispensing device 170, as indicated by arrow 172. In some examples, fuel tank 144 may be configured to store fuel received from fuel dispensing device 170 until the fuel is supplied to engine 110 for combustion. In some examples, control system 190 may receive an indication of the level of fuel stored in fuel tank 144 via a fuel level sensor. The level of fuel stored at fuel tank 144 (e.g., as indicated by the fuel level sensor) may be communicated to the vehicle driver, for example, via a fuel gauge or an indication in vehicle instrument panel 196.

[0042] The vehicle propulsion system 100 may also include an ambient temperature / humidity sensor 198, and roll stability control sensors, such as one or more lateral and / or longitudinal and / or yaw rate sensors 199. The vehicle instrument panel 196 may include one or more indicator lights and / or a text-based display in which messages are displayed to the driver. The vehicle instrument panel 196 may also include various input portions for receiving driver input, such as buttons, a touch screen, voice input / recognition, etc. For example, the vehicle instrument panel 196 may include a refuel button 197 that can be manually actuated or pressed by the vehicle driver to initiate a refuel. For example, in response to the vehicle driver actuating the refuel button 197, the fuel tank in the vehicle may be depressurized, allowing the refueling to be performed.

[0043] In some examples, vehicle propulsion system 100 may include one or more onboard cameras 135. For example, onboard cameras 135 may transmit photographic and / or video images to control system 190. For example, in some examples, onboard cameras may be configured to record images within a predetermined radius of the vehicle.

[0044] The control system 190 can be communicatively coupled to other vehicles or infrastructure using appropriate communication technologies. For example, the control system 190 can be coupled to other vehicles or infrastructure via a wireless network 131, which may include Wi-Fi, Bluetooth, a cellular service, a wireless data transmission protocol, or the like. The control system 190 can broadcast (and receive) information about vehicle data, vehicle diagnostics, traffic conditions, vehicle location information, vehicle operating procedures, and the like via vehicle-to-vehicle (V2V), vehicle-to-infrastructure-to-vehicle (V2I2V), and / or vehicle-to-infrastructure (V2I or V2X) technologies. Communications between vehicles and the information exchanged between vehicles can be direct between vehicles or can be multi-hop. In some examples, longer-range communications (e.g., WiMax) can be used in conjunction with V2V or V2I2V to extend coverage by several miles. In still other examples, the vehicle control system 190 may be communicatively coupled to other vehicles or infrastructure via the wireless network 131 and the Internet (eg, the cloud), as is generally known in the art.

[0045] The vehicle system 100 may also include an onboard navigation system 132 (e.g., a global positioning system) with which the vehicle driver can interact. The navigation system 132 may include one or more position sensors to help estimate vehicle speed, vehicle altitude, vehicle heading / position, etc. This information may be used to infer engine operating parameters, such as local atmospheric pressure. As discussed above, the control system 190 may be further configured to receive information via the Internet or other communication networks. Information received from the GPS may be cross-referenced with information available via the Internet to determine local weather conditions, local vehicle regulations, etc. In some examples, the vehicle system 100 may include laser, radar, sonar, acoustic sensors 133 that may enable the collection of vehicle location, traffic information, etc., via the vehicle.

[0046] Figure 2 A schematic depiction of a vehicle system 206 is shown. It is understood that the vehicle system 206 may include Figure 1 The vehicle system 206 is the same vehicle system as the vehicle system 100 depicted herein. The vehicle system 206 includes an engine system 208 coupled to an emission control system (evaporative emission system) 251 and a fuel system 218. It will be appreciated that the fuel system 218 may include Figure 1 1. The vehicle system 206 is similar to the fuel system 140 depicted herein. Emission control system 251 includes a fuel vapor container or canister 222 that can be used to capture and store fuel vapors. In some examples, vehicle system 206 can be a hybrid electric vehicle system. However, it will be understood that the description herein may refer to a non-hybrid vehicle, e.g., one equipped with an engine without a motor operable to at least partially propel the vehicle, without departing from the scope of this disclosure.

[0047] Engine system 208 may include engine 110 having a plurality of cylinders 230. Engine 110 includes an engine intake passage 223 and an engine exhaust passage 225. Engine intake passage 223 includes a throttle valve 262, which is in fluid communication with an engine intake manifold 244 via an intake passage 242. Furthermore, engine intake passage 223 may include an air box and a filter (not shown) positioned upstream of throttle valve 262. Engine exhaust system 225 includes an exhaust manifold 248, which leads to an exhaust passage 235 that directs exhaust gas to the atmosphere. Engine exhaust system 225 may include one or more exhaust catalysts 270 that may be mounted in a close-coupled position within the exhaust system. In some examples, an electric heater 298 may be coupled to the exhaust catalyst and used to heat the exhaust catalyst to a predetermined temperature (e.g., a light-off temperature) or above a predetermined temperature. One or more emission control devices may include a three-way catalyst, a lean NOx trap, a diesel particulate filter, an oxidation catalyst, and the like. It should be understood that the engine may include other components, such as various valves and sensors. For example, an atmospheric pressure sensor 213 may be included in the engine intake. In one example, atmospheric pressure sensor 213 may be a manifold air pressure (MAP) sensor and may be coupled to the engine intake downstream of throttle 262. Atmospheric pressure sensor 213 may rely on a partially open throttle state or a fully or wide-open throttle state, such as when throttle 262 is opened by an amount greater than a threshold, to accurately determine atmospheric pressure.

[0048] The fuel system 218 may include a fuel tank 220 coupled to a fuel pump system 221. It will be appreciated that the fuel tank 220 may include the same fuel pump system as described above. Figure 1144 is depicted at 110. In one example, fuel tank 220 comprises a steel fuel tank. In some examples, the fuel system may include a fuel tank temperature sensor 296 for measuring or inferring the fuel temperature. Fuel pump system 221 may include one or more pumps for pressurizing fuel for delivery to injectors of engine 110, such as exemplary injector 266 shown. Although only a single injector 266 is shown, additional injectors may be provided for each cylinder. It should be understood that fuel system 218 may be a returnless fuel system, a return fuel system, or various other types of fuel systems. Fuel tank 220 may hold a variety of fuel mixtures, including fuels with a range of alcohol concentrations, such as various gasoline-ethanol blends, including E10, E85, gasoline, and combinations thereof. A fuel level sensor 234 located in fuel tank 220 may provide an indication of the fuel level ("fuel level input") to controller 212. As depicted, fuel level sensor 234 may include a float connected to a variable resistor. Alternatively, other types of fuel level sensors may be used.

[0049] Vapors generated in fuel system 218 may be routed to evaporative emission control system (hereinafter referred to as evaporative emission system) 251, which includes fuel vapor canister 222, via vapor recovery line 231 before being purged into engine intake 223. Vapor recovery line 231 may be coupled to fuel tank 220 via one or more conduits and may include one or more valves for isolating the fuel tank during certain conditions. For example, vapor recovery line 231 may be coupled to fuel tank 220 via one or more of conduits 271, 273, and 275, or a combination thereof.

[0050] Furthermore, in some examples, one or more fuel tank vent valves may be positioned in conduits 271, 273, or 275. Among other functions, the fuel tank vent valves may allow the fuel vapor canister of the emission control system to be maintained at a low pressure or vacuum without increasing the rate at which fuel evaporates from the tank (which would otherwise occur if the fuel tank pressure were reduced). For example, conduit 271 may include a grade vent valve (GVV) 287, conduit 273 may include a fill limit venting valve (FLVV) 285, and conduit 275 may include a grade vent valve (GVV) 283. Furthermore, in some examples, recycle line 231 may be coupled to fuel refueling system 219. In some examples, the fuel refueling system may include a fuel cap 205 for sealing the fuel refueling system from the atmosphere. Fuel refueling system 219 is coupled to fuel tank 220 via fuel refueling pipe or neck 211.

[0051] In addition, refueling system 219 may include a refueling lock 245. In some examples, refueling lock 245 may be a fuel cap locking mechanism. The fuel cap locking mechanism may be configured to automatically lock the fuel cap in a closed position so that the fuel cap cannot be opened. For example, fuel cap 205 may remain locked via refueling lock 245 while the pressure or vacuum in the fuel tank is greater than a threshold value. In response to a refueling request, such as a request initiated by the vehicle driver, the fuel tank may be depressurized and unlocked after the pressure or vacuum in the fuel tank drops below a threshold value. The fuel cap locking mechanism may be a latch or clutch that prevents the fuel cap from being removed when engaged. The latch or clutch may be electrically locked, such as by a solenoid, or may be mechanically locked, such as by a pressure diaphragm.

[0052] In some examples, refuel lock 245 may be a filler pipe valve located at the mouth of fuel filler pipe 211. In such examples, refuel lock 245 may not prevent removal of fuel cap 205. Instead, refuel lock 245 may prevent insertion of a refuel pump into fuel filler pipe 211. The filler pipe valve may be electrically locked, such as by a solenoid, or mechanically locked, such as by a pressure diaphragm.

[0053] In some examples, refuel lock 245 can be a refuel door lock, such as a latch or clutch, that locks a refuel door located in a body panel of the vehicle. The refuel door lock can be electrically locked, such as by a solenoid, or mechanically locked, such as by a pressure diaphragm.

[0054] In the example where an electric mechanism is used to lock refuel lock 245, refuel lock 245 may be unlocked by a command from controller 212 (e.g., when the fuel tank pressure drops below a pressure threshold). In the example where a mechanical mechanism is used to lock refuel lock 245, refuel lock 245 may be unlocked by a pressure gradient (e.g., when the fuel tank pressure drops to atmospheric pressure).

[0055] Emission control system 251 may include one or more emission control devices, such as one or more fuel vapor canisters 222, as discussed. The fuel vapor canister may be filled with a suitable adsorbent 286b such that the canister is configured to temporarily capture fuel vapors (including evaporated hydrocarbons) during fuel tank refill operations and during diagnostic routines, as discussed in detail below. In one example, the adsorbent 286b used is activated carbon. Emission control system 251 may also include a canister vent path or vent line 227 that directs gas from canister 222 to the atmosphere when storing or capturing fuel vapors from fuel system 218.

[0056] The charcoal canister 222 may include a buffer zone 222a (or buffer area), each of which includes an adsorbent. As shown, the volume of the buffer zone 222a may be smaller than the volume of the charcoal canister 222 (e.g., be a portion thereof). The adsorbent 286a in the buffer zone 222a may be the same as or different from the adsorbent in the charcoal canister (e.g., both may include charcoal). The buffer zone 222a may be positioned within the charcoal canister 222 so that during canister loading, fuel tank vapors are first adsorbed within the buffer zone, and then when the buffer zone is saturated, additional fuel tank vapors are adsorbed in the charcoal canister. In contrast, during canister cleaning, fuel vapors are first desorbed from the charcoal canister (e.g., to a threshold amount) and then desorbed from the buffer zone. In other words, the loading and unloading of the buffer zone is not consistent with the loading and unloading of the charcoal canister. Therefore, the role of the charcoal canister buffer zone is to slow down any sudden increase in fuel vapor flowing from the fuel tank to the charcoal canister, thereby reducing the possibility of any sudden increase in fuel vapor entering the engine. One or more temperature sensors 232 may be coupled to the charcoal canister 222 and / or coupled within it. When the adsorbent in the canister adsorbs fuel vapor, heat (adsorption heat) is generated. Similarly, when the adsorbent in the canister desorbs fuel vapor, heat is consumed. In this way, the adsorption and desorption of fuel vapor by the canister can be monitored, and the canister load can be estimated based on temperature changes within the canister.

[0057] Vent line 227 may also allow fresh air to be drawn into canister 222 when purging stored fuel vapors from fuel system 218 to engine intake 223 via purge line 228 and purge valve 261. For example, purge valve 261 may be normally closed but may be opened during certain conditions to provide vacuum from engine intake manifold 244 to the fuel vapor canister for purging. In some examples, vent line 227 may include an air filter 259 positioned upstream of canister 222.

[0058] In some examples, the flow of air and vapor between canister 222 and the atmosphere can be regulated by a canister vent valve 297 coupled within vent line 227. When included, canister vent valve 297 can be a normally open valve, allowing fuel tank isolation valve (FTIV) 252 to control communication between fuel tank 220 and the atmosphere. FTIV 252 can be positioned within conduit 278 between the fuel tank and fuel vapor canister 222. FTIV 252 can be a normally closed valve that, when open, allows fuel vapors to vent from fuel tank 220 to fuel vapor canister 222. The fuel vapors can then be vented to the atmosphere or purged into engine air intake 223 via canister purge valve 261.

[0059] In some examples, vent line 227 may include a hydrocarbon sensor 295. Such a hydrocarbon sensor may be configured to monitor for the presence of hydrocarbons in the vent line and, if detected, take mitigating measures to prevent unwanted vent emissions from reaching the atmosphere.

[0060] The fuel system 218 can be operated in a variety of modes by the controller 212 by selectively adjusting various valves and solenoids. It will be appreciated that the control system 214 may include the same Figure 1 For example, the fuel system may be operated in a fuel vapor storage mode (e.g., during a fuel tank refueling operation and when the engine is not combusting air and fuel), wherein controller 212 may open isolation valve 252 (when included) while closing canister purge valve (CPV) 261 to direct refueling vapors into canister 222 while preventing fuel vapors from being directed into the intake manifold.

[0061] As another example, the fuel system can be operated in a refueling mode (e.g., when a vehicle operator requests refueling of the fuel tank), wherein controller 212 can open isolation valve 252 (when included) while maintaining canister purge valve 261 closed to depressurize the fuel tank before allowing fuel to be added to the fuel tank. In this way, isolation valve 252 (when included) can remain open during the refueling operation to allow refueling vapors to be stored in the canister. After refueling is complete, the isolation valve can be closed.

[0062] As another example, the fuel system can be operated in a canister purge mode (e.g., after the emission control device light-off temperature has been reached and the engine is burning air and fuel), wherein controller 212 can open canister purge valve 261 while closing isolation valve 252 (when included). Here, vacuum generated by intake manifold 244 of the operating engine can be used to draw fresh air through ventilation passage 227 and through fuel vapor canister 222 to purge stored fuel vapor into intake manifold 244. In this mode, fuel vapor purged from the canister is combusted in the engine. Purge can continue until the amount of fuel vapor stored in the canister is below a threshold. In some examples, purge can also include commanding the FTIV to open so that fuel vapor from the fuel tank can be drawn into the engine for combustion.

[0063] The control system 214 is shown as receiving information from a plurality of sensors 216 (various examples of which are described herein) and sending control signals to a plurality of actuators 281 (various examples of which are described herein). As one example, the sensors 216 may include: an exhaust gas sensor 237 located upstream of the emission control device 270; a temperature sensor 233; a pressure sensor 291; a pressure sensor 282; and a canister temperature sensor 232. Other sensors (such as pressure, temperature, air-fuel ratio, and composition sensors) may be coupled to various locations in the vehicle system 206. As another example, the actuators may include a throttle 262, a fuel tank isolation valve 252, a canister purge valve 261, and a canister vent valve 297. The control system 214 may include a controller 212. The controller may receive input data from the various sensors, process the input data, and trigger the actuators in response to the processed input data based on instructions or code programmed therein corresponding to one or more routines. Figures 4 and 5 and Figures 7 to 10 An exemplary control routine is described.

[0064] In some examples, the controller may be placed in a reduced power mode or sleep mode, in which the controller maintains only basic functionality and operates with lower battery consumption than in a corresponding wake-up mode. For example, the controller may be placed in sleep mode after a vehicle stop event so that a diagnostic routine can be performed for a certain duration after the vehicle stop event. The controller may have a wake-up input that allows the controller to return to wake-up mode based on input received from one or more sensors or via the expiration of a timer, the timer being set so that when the timer expires, the controller returns to wake-up mode. In some examples, the opening of a vehicle door may trigger a return to wake-up mode. In other examples, the controller may need to be awake in order to perform such methods. In such examples, the controller may remain awake for a period of time (the duration being referred to as the time period that the controller remains awake to perform the long-term shutdown function) so that the controller can be awake to perform the evaporative emissions test diagnostic routine.

[0065] Controller 212 may intermittently perform an undesirable evaporative emissions detection routine on fuel system 218 and / or evaporative emissions system 251 to confirm the absence of undesirable evaporative emissions from the fuel system and / or evaporative emissions system. Thus, the evaporative emissions detection routine (engine-off test) may be performed while the engine is off, utilizing engine-off natural vacuum (EONV) generated by changes in fuel tank temperature and pressure following a drive cycle after engine shutdown. However, for hybrid vehicle applications, there may be limited engine run time, which may result in an EONV test that may not be robust due to the lack of heat rejection from the engine to the fuel tank. Similarly, the evaporative emissions detection routine may be performed while the engine is running by purging the evaporative emissions system and / or fuel system using engine intake manifold vacuum, but such opportunities may be rare in hybrid vehicle applications.

[0066] Thus, in some examples, the undesirable evaporative emissions detection routine may include a vacuum pump. For example, in some examples, the evaporative emissions test diagnostic may include an evaporative level check module (ELCM) (not shown) communicatively coupled to controller 212. Such an ELCM may be coupled to vent 227 between canister 222 and the atmosphere. Such an ELCM may include a vacuum pump for applying negative pressure to the fuel system and / or evaporative emissions system when testing for the presence or absence of undesirable evaporative emissions. Such an ELCM may further include a reference orifice and a pressure sensor. Thus, a baseline check may be performed, wherein a vacuum may be drawn on the reference orifice. Following the baseline check, the fuel system and / or evaporative emissions system may be evacuated via the ELCM vacuum pump such that, in the absence of undesirable evaporative emissions, the vacuum may be reduced to a baseline check vacuum level.

[0067] However, the inventors herein have recognized that using an ELCM such as that described above can increase manufacturing costs, which may be desirable to avoid. Therefore, to perform the undesirable evaporative emissions testing procedure, a vacuum pump 289 may be positioned in vacuum pump conduit 294. The vacuum pump may include a rotary vane pump, a diaphragm pump, a liquid ring pump, a piston pump, a scroll pump, a screw pump, a Wankel pump, or the like, and may be understood to be connected in parallel with CVV 297. The vacuum pump conduit 294 may be configured to direct a fluid flow (e.g., air and fuel vapor) from vent line 227 to around canister vent valve 297. The vacuum pump conduit 294 may include a first check valve (CV1) 292 and a second check valve (CV2) 293. When vacuum pump 289 is activated, air may be drawn from vent line 227 between canister 222 and CVV 297, through vacuum pump conduit 294, and returned to vent line 227 at a location between canister vent valve 297 and atmosphere. In other words, the vacuum pump can be activated to evacuate evaporative emissions system 251, and further evacuate fuel system 218, if FTIV 252 is commanded to open via the controller. CV1 292 may include a pressure / vacuum actuated valve that can open in response to activation of the vacuum pump to evacuate the fuel system and / or the evaporative emissions system, and can close in response to deactivation or shutdown of vacuum pump 289. Similarly, CV2 may include a pressure / vacuum actuated valve. When vacuum pump 289 is activated to evacuate the fuel system and / or the evaporative emissions system, CV2 293 can open to allow fluid flow from vacuum pump conduit 294 to atmosphere, and can close in response to shutdown of vacuum pump 289. It will be appreciated that CVV 297 can be commanded to close in order to evacuate the fuel system and / or the evaporative emissions system via vacuum pump 289.

[0068] As discussed above, the ELCM may include a reference orifice that enables determination of a vacuum level that, if reached when purging the fuel system and / or the evaporative emissions system, indicates the absence of undesirable evaporative emissions. However, in vehicle systems 206 that do not include an ELCM but include vacuum pump 289, the reference orifice may not be present. Therefore, additional calibration means may be utilized to determine a vacuum threshold value that indicates the presence or absence of undesirable evaporative emissions. For example, a 3D lookup table stored at the controller may be present that enables determination of the threshold value based on ambient temperature and fuel level. In this way, the reference orifice may not be included, which may reduce the costs associated with including the ELCM.

[0069] Furthermore, as discussed, the ELCM may include a pressure sensor. In the exemplary vehicle system 206, a pressure sensor 282 is included, positioned in conduit 278. Thus, it can be understood that the FTIV 252 is defined by the fuel tank pressure sensor 291 (fuel tank pressure transducer) and the pressure sensor 282 positioned in conduit 278 between the FTIV 252 and the charcoal canister 222. In this manner, in a closed state, the pressure sensor 282 can monitor the pressure in the evaporative emission system, and the pressure sensor 291 can monitor the pressure in the fuel system.

[0070] Thus, by using vacuum pump 289 in conjunction with pressure sensor 282 in vacuum pump conduit 294 (which includes CV1 292 and CV2 293 ), manufacturing costs associated with including devices for purging the fuel system and evaporative emissions system during engine off conditions may be reduced.

[0071] As discussed, CVV 297 can be used to regulate the flow of air and vapor between canister 222 and the atmosphere and can be controlled during or prior to a diagnostic routine. For example, when a CVV is included, the CVV can be opened during fuel vapor storage operations (e.g., during fuel tank refueling) to allow air stripped of fuel vapor after passing through the canister to be pushed to the atmosphere. Similarly, during purge operations (e.g., during canister regeneration and while the engine is running), the CVV can be opened to allow fresh air flow to strip fuel vapor stored in the canister. In the exemplary vehicle system 206, the configuration of vacuum pump 289 positioned in vacuum pump conduit 294 can allow purge and refueling operations to be performed without undesirable additional restrictions (pump 289 and check valves CV1, CV2). In other words, during purge and refueling operations, the CVV can be commanded open, wherein fluid flow through vacuum pump conduit 294 can be prevented via check valves (CV1, CV2) in the event that vacuum pump 289 is deactivated.

[0072] In some examples, the CVV 297 can be a solenoid valve, wherein the valve is opened or closed via actuation of a canister vent solenoid. In particular, the canister vent valve can be a normally open valve that closes when the canister vent solenoid is actuated. In some examples, the CVV 297 can be configured as a latchable solenoid valve. In other words, when the valve is in a closed configuration, it latches in the closed state without requiring additional current or voltage. For example, the valve can be closed with a 100ms pulse and then opened with another 100ms pulse at a later point in time. In this way, the battery power required to maintain the CVV closed can be reduced.

[0073] Thus, an example of a test diagnostic for determining the presence or absence of undesirable evaporative emissions using vacuum pump 289 may include closing the CVV and CPV and activating the vacuum pump to evacuate the evaporative emissions system with the FTIV closed. If a threshold vacuum is reached (monitored via pressure sensor 282), this may indicate the absence of severe undesirable evaporative emissions. In response to indicating the absence of severe undesirable evaporative emissions, vacuum pump 289 may be stopped or deactivated. With vacuum pump 289 deactivated, CV1 292 (and CV2 293) may be closed, thereby isolating the evaporative emissions system from the atmosphere. In response to isolating the evaporative emissions system from the atmosphere, a pressure loss may be monitored, and if the pressure loss is below a pressure loss threshold, or if the pressure loss rate is less than a pressure loss rate threshold, this may indicate the absence of non-severe undesirable evaporative emissions in the evaporative emissions system.

[0074] In a similar manner, vacuum pump 289 can be used to evacuate the fuel system while the FTIV is open (e.g., actuated open via a command from a controller). If a threshold vacuum is reached (monitored via pressure sensor 282 or fuel tank pressure sensor 291), the absence of significant, undesirable evaporative emissions can be indicated. In response to the indication that significant, undesirable evaporative emissions from the fuel system are absent, the fuel system can be sealed by commanding the FTIV closed (e.g., actuated closed via a command from a controller), and pressure loss in the fuel system can be monitored. In response to an indication that the pressure loss is less than a pressure loss threshold, or if the pressure loss rate is less than a pressure loss rate threshold, the absence of non-severe, undesirable evaporative emissions from the fuel system can be indicated (provided the evaporative emissions system is known to be free of undesirable evaporative emissions).

[0075] However, as discussed above, there may be situations where pressure loss may be adversely affected by fuel evaporation. For example, at high ambient temperatures or high fuel temperatures, fuel evaporation may significantly contribute to the loss, which may confuse the interpretation of diagnostics and, in some examples, may result in false faults or an indication that unwanted evaporative emissions are present when in fact, the fuel system and / or evaporative emissions system does not. The inventors herein have recognized these issues and have developed methods to avoid them, as will be discussed below with respect to Figures 4 and 5 and Figures 7 to 10Discussed in detail. Briefly, such a method may include evacuating the fuel system and / or evaporative emissions system to a variable level of target vacuum (e.g., a negative pressure relative to atmospheric pressure), wherein the variable level of target vacuum is a function of ambient temperature and canister loading. For example, consider a scenario where the ambient temperature is high (e.g., 90°F) but the canister loading is low (e.g., 10% full or underfilled with fuel vapor). In this scenario, a greater vacuum (e.g., a more negative vacuum relative to atmosphere) may be drawn on the fuel system and / or evaporative emissions system than in a scenario where the temperature is low (e.g., 50°F), such that a greater "signal-to-noise ratio" may be present for the bleed portion of the test. In other words, by drawing a greater vacuum in the case of high ambient temperature, even if the high ambient temperature causes fuel evaporation that resists the vacuum after the fuel system and / or evaporative emissions system is sealed from the atmosphere, such fuel evaporation may not adversely affect the results of the diagnostic.

[0076] In some examples of vehicles where the fuel tank is sealed except during refueling events and certain diagnostic routines, an undesirable evaporative emissions detection routine performed on a sealed fuel system may include an indication of a standing pressure or vacuum in the fuel system greater than a threshold pressure in the absence of pressure or vacuum introduced from a pump or engine intake manifold vacuum, etc. However, there may be situations where the absence of standing pressure or vacuum may not be the result of the presence of undesirable evaporative emissions or the result of ambient temperature and vehicle operating conditions causing the fuel system to not maintain pressure or vacuum above a threshold. For example, during the course of a diurnal cycle, temperature fluctuations may result in a situation where the fuel system does not maintain pressure or vacuum. In such situations, as discussed above, there may be an opportunity to perform a vacuum pump based test for undesirable evaporative emissions. However, such an action may not always be desirable because the action of evacuating the fuel system via the vacuum pump may draw fuel vapors into the canister 222, which may result in further loading of the fuel vapor canister. The inventors have recognized this problem and have developed a method to address this problem, which is discussed below with respect to Figures 3 and 4 and Figure 7 Detailed discussion follows. Briefly, a method may include: maintaining a fuel system seal in the event that the fuel system does not maintain a pressure or vacuum greater than a threshold pressure or vacuum; retrieving data related to fuel tank pressure from a population of vehicles within a predetermined distance of a vehicle being diagnosed; and, in response to the fuel tank pressure from the population of vehicles correlating (e.g., within 5%) with the fuel tank pressure from the vehicle being diagnosed, indicating the absence of fuel tank degradation. In this manner, the vehicle fuel system may be diagnosed without further loading the fuel vapor canister. This method may be particularly useful in situations where ambient temperature is high and the canister load is high, as discussed in greater detail below.

[0077] In yet another example, there may be an opportunity to test for undesirable evaporative emissions from the fuel system and / or evaporative emissions system by evacuating the fuel system and / or evaporative emissions system just before a key-off event while the vehicle is in operation. In such an example, the vehicle controller may be configured to learn common routes that the vehicle travels and, therefore, may indicate the expected duration of a key-off event along a particular route that the vehicle is traveling. In one example, it may be desirable to test for undesirable evaporative emissions, but if an EONV test or other vacuum pump-based diagnostic test is being performed, the vehicle may be restarted before the test is complete, which may adversely affect the completion rate of such diagnostic test. Therefore, if a key-off event is predicted or inferred to have a specific duration during which an EONV test or other vacuum pump-based diagnostic test is undesirable (e.g., if the controller wakes the vehicle a predetermined duration after key-off for testing), there may be an opportunity to evacuate the fuel system and / or evaporative emissions system just before the key-off event. In this manner, at key-off, the fuel system and / or evaporative emissions system can be sealed and pressure loss monitored to infer the presence or absence of less severe, undesirable evaporative emissions from the fuel system and / or evaporative emissions system. It will be appreciated that in this approach, a vacuum pump can be used to evacuate the fuel system and / or evaporative emissions system just prior to key-off when the vehicle is propelled in an electric-only operating mode. Furthermore, similar to the discussion above, the vacuum drawn from the fuel system and / or evaporative emissions system can include a variable target vacuum based on ambient temperature and canister loading.

[0078] Therefore, now turn to Figure 3 , depicts an exemplary diagram 300 detailing how a vehicle undergoing fuel system diagnostics (referred to herein as a diagnosed vehicle, or VD) may obtain population information to determine the presence or absence of undesirable evaporative emissions from the VD's fuel system, the population information comprising one or more data sets relating to fuel tank pressures in vehicles similar to the VD. For example, the inventors herein have recognized that it may be desirable to utilize population information from multiple vehicles in order to confirm the presence of undesirable evaporative emissions from a vehicle's fuel system. In this way, fuel system integrity may be diagnosed without venting the fuel tank and without using an onboard pump, which may be used to reduce the chance of loading the canister, reduce battery usage, and the like. Such population information may include, for example, one or more of a vehicle-to-vehicle (V2V) network or a vehicle-to-infrastructure-to-vehicle (V2I2V) network. Thus, Figure 3A vehicle 310 (VD 310) is shown in wireless communication 312 (eg, V2V) with a plurality of other vehicles 315 to be diagnosed for the presence or absence of undesirable evaporative emissions from a fuel system. It will be appreciated that the vehicle 310 may include Figure 1 The vehicle propulsion system 100 depicted therein and / or Figure 2 The vehicle 310 may include a control system 214 that includes a controller 212, as described above with respect to the vehicle system 206. Figure 2 As discussed, wireless communication device 280 may be coupled to controller 212 for enabling wireless communication between vehicle 310 and vehicle 315. Additionally, vehicle 310 may include navigation device 132 (e.g., GPS), wherein the navigation device may be configured to receive information via GPS satellites 323.

[0079] Although not explicitly shown, it is understood that other vehicles 315 may also include components as described for vehicle 310. For example, vehicle 315 may similarly include a control system in which a controller receives information from a plurality of sensors and in which commands may be sent from the controller to a plurality of actuators. Furthermore, vehicle 315 may include wireless communication devices for sending and receiving wireless communications between vehicles or infrastructure.

[0080] Vehicle 310 may wirelessly transmit information via V2V or V2I2V technology and retrieve information from vehicles 315 that are within a predetermined distance 320 from vehicle 310. For example, vehicles 327 (where vehicles 327 are a subset of vehicles 315) may be excluded from having information retrieved from these vehicles because they are outside of predetermined distance 320 from vehicle 310. In some examples, the predetermined distance may be set such that the vehicle from which information / data is to be retrieved is likely experiencing very similar ambient temperature / humidity and very similar weather as the diagnosed vehicle (e.g., 310).

[0081] Of the vehicles within a predetermined distance 320 from the vehicle to be diagnosed 310, it may be further determined which vehicles' information / data are to be utilized. In other words, of the vehicles within a predetermined distance 320 from the vehicle to be diagnosed 310, only a subset of these vehicles may constitute a selected group or groups 324 from which one or more data sets related to fuel tank pressure may be retrieved to determine the presence or absence of undesirable evaporative emissions from the fuel system of the VD. Figure 7The presented method elaborates on the details of what may constitute such a selected group 324. Briefly, the selection criteria for group 324 may be based on: vehicle make / model (e.g., a make / model similar to the diagnosed vehicle); whether the vehicle's fuel tank comprises a sealed fuel tank; a fuel level within a predetermined fuel level range; whether the vehicle is near structures that may affect the temperature / environmental conditions experienced by the vehicle; whether the vehicle is in a key-off state; the time since key-off; the fuel tank temperature; the engine run time before the key-off event; etc. Thus, vehicles within the predetermined distance 320 that are not identified as constituting the selected group 324 may be referred to as excluded vehicles 329.

[0082] After identifying the selected group 324, one or more data sets including information related to fuel tank pressure may be retrieved from vehicle 315 by vehicle 310 via V2V or V2I2V technology. In one example, fuel tank pressure data may be obtained from each of the vehicles (e.g., 310 and 315) for a predetermined time range. More specifically, it will be appreciated that for vehicles with sealed fuel tanks, temperature fluctuations over a 24-hour period (e.g., a diurnal cycle) may cause pressure variations within such sealed fuel tanks. Therefore, by retrieving data related to fuel tank pressure from each vehicle (e.g., 310, 315) over a predetermined time range, a pattern (e.g., direction and magnitude) of fuel tank pressure may be obtained. In some examples, the controller of vehicle 310 may average the fuel tank pressure data to derive an average fuel tank pressure for the selected group 324. Next, information regarding the direction (e.g., positive pressure relative to the atmosphere or negative pressure relative to the atmosphere) and magnitude (e.g., how much positive or negative) of the fuel tank pressure corresponding to the selected group 324 may be compared (via a controller of the vehicle 310) with data obtained regarding the fuel tank pressure of the diagnosed vehicle 310. If the fuel tank pressure data obtained from the diagnosed vehicle 310 correlates with the fuel tank pressure data obtained from the selected group 324, it may be determined that no undesirable evaporative emissions are originating from the fuel tank of the diagnosed vehicle 310. In this example, "correlating" the fuel tank pressure data from the selected group 324 with the fuel tank pressure data from the diagnosed vehicle 310 may include the fuel tank pressure data from the diagnosed vehicle 310 being within a predetermined threshold (e.g., within 5% or less) of the fuel tank pressure data from the vehicles comprising the selected group. However, if the fuel tank pressure in the diagnosed vehicle 310 does not correlate with the fuel tank pressure data obtained from the selected group 324 (e.g., differs by more than 5%), it may be determined that undesirable evaporative emissions are present from the fuel system of the diagnosed vehicle 310.

[0083] It is understandable that the above Figure 3The described method can be applied to a vehicle that is in a key-off state and is not being propelled by an onboard energy storage device (such as a battery) or by the vehicle's engine. For example, if the vehicle is in operation, then even if the engine is not operating, driving conditions can cause significant fuel slosh events in the fuel tank, which can contribute to pressure variations as indicated by the FTPT. Such driving-condition-based pressure variations can significantly contribute to adding a noise factor to any analysis of population-based fuel tank diagnostics, making such an approach prone to error. As such, it will be understood that the method described herein relates to a vehicle in a key-off state, and not to a vehicle that is in operation.

[0084] therefore, Figure 3 The general method described constitutes a high-level exemplary illustration of how fuel system diagnostics can be performed based on swarm information obtained via V2V or V2I2V technology. Figure 4 and Figure 7 This method is further discussed.

[0085] Now turn Figure 4 , shows a high-level flow chart for determining whether to perform a variable vacuum-based diagnostic for undesirable evaporative emissions or a population-based fuel system diagnostic. More specifically, method 400 may be utilized in response to a key-off event to indicate a canister load status and retrieve forecast weather conditions. Based on the indicated canister load status and the retrieved forecast weather conditions, a determination may be made as to whether to perform a variable vacuum-based test or continue with a population-based fuel system diagnostic. Reference will be made to Figures 1 to 3 Method 400 is described with reference to the system described in

[0045] , but it should be understood that method 400 may be applied to other systems without departing from the scope of this disclosure. Method 400 may be implemented by a controller, such as controller 212, and may be stored as executable instructions in a non-transitory memory. Instructions for implementing method 400 and the remaining methods included herein may be executed by the controller based on instructions stored on the controller's memory and in conjunction with signals received from sensors of the vehicle system, such as the sensors described above with reference to

[0046] Figures 1 to 3 The controller may employ fuel system and evaporative emission system actuators, such as the FTIV (eg, 252 ), vacuum pump (eg, 289 ), CVV (eg, 297 ), etc., according to the methods described below.

[0086] Method 400 begins at 405 by evaluating current vehicle operating conditions. Operating conditions can be estimated, measured, and / or inferred and may include: environmental conditions, such as temperature, humidity, barometric pressure, etc.; engine conditions, such as engine operating state, engine speed, engine load, etc.; and fuel system conditions, such as fuel level, fuel tank pressure, etc. Continuing at 410, method 400 may include indicating whether a key-off event is indicated. A key-off event may be understood as an event in which a vehicle system is deactivated or shut down. If a key-off event is not indicated at 410, method 400 may proceed to 415. At 415, method 400 may include maintaining the current vehicle operating conditions. For example, if the vehicle is operating with the engine running, the engine may remain in its current operating state. If the vehicle is being propelled at least partially via the motor, such conditions may be maintained, and so on. Method 400 may then end.

[0087] Returning to 410 , in response to indicating a key-off event, method 400 may proceed to 420 . At 420 , method 400 may include retrieving or indicating a fuel vapor canister charge status. As discussed, as an example, the charge status may be inferred via one or more temperature sensors (e.g., 232 ) located in the canister. In response to retrieving the canister charge status, method 400 may proceed to 425 . At 425 , method 400 may include obtaining forecast weather conditions. For example, control system 214 (e.g., 190 ) may be configured to receive information via the internet or other communication network to obtain weather information in the vicinity of the VD, where the vicinity of the VD may include weather information within a predetermined distance of the VD (in all directions). This weather information may be retrieved from one or more data servers, including government and / or private data collection services that provide forecast weather data in a retrievable format. In some examples, the weather information may be based on the vehicle's location, as determined by an onboard GPS. The retrieved weather data may include forecasted temperature, humidity, barometric pressure, precipitation, wind, etc. It will be appreciated that such retrieved forecast weather information can be transmitted to a vehicle controller where the data can be processed by the controller. In one example, the retrieved weather information or data can include weather information forecasted for the next 24 hours. In other examples, shorter or longer periods of forecast weather information can be retrieved.

[0088] In the event that the canister loading status and forecast weather conditions are retrieved via the controller, method 400 may proceed to 430. At 430, method 400 may include indicating whether a condition for performing a variable vacuum diagnostic is satisfied. The condition for performing a variable vacuum diagnostic may be satisfied including an indication that a predetermined amount of time has elapsed since a previous diagnosis of the presence or absence of undesirable evaporative emissions from the fuel system and / or the evaporative emissions system. The condition for performing a variable vacuum diagnostic may be satisfied including an indication that a key-off event is likely to include a duration greater than a predetermined duration threshold. For example, the predetermined duration threshold may include an amount of time sufficient to perform a variable vacuum diagnostic (which may include putting the controller to sleep for a certain duration and then waking the controller to perform the diagnostic). In some examples, a route learning method (described below in Figure 8 ) to infer whether a particular key-off event is likely to be greater than or predicted to be greater than a predetermined duration threshold.

[0089] Conditions for variable vacuum diagnostics may also include vehicle controller interrogation Figure 6 A lookup table 600 is depicted therein. Figure 6 Depicted is a 3D lookup table that may be stored at a controller that may indicate a target vacuum to which the fuel system and / or evaporative emissions system is to be pulled down for a variable vacuum diagnostic based on the canister loading state and the ambient temperature. Specifically, there may be situations where performing a variable vacuum diagnostic is undesirable because doing so may undesirably load the canister to a point where blow-through emissions are likely to occur. In other words, performing a variable vacuum diagnostic may include commanding the FTIV to open and evacuate the fuel system to a variable vacuum level based on the canister loading state and the ambient temperature (or in some examples, the fuel temperature), and therefore there may be situations where such action is undesirable because fuel vapors from the fuel tank may load the canister to a point where blow-through emissions are likely to occur. Figure 6 , one example may include a scenario where the canister is 80% full and the ambient temperature is anywhere from 50°F to 59°F. Another example may include a scenario where the canister is 70% full and the ambient temperature is anywhere from 70°F to 79°F. It will be appreciated that Figure 6 Such examples shown herein are intended to be illustrative, and it will be further understood that such values ​​may be different for various canister sizes, as the values ​​may vary depending on, among other things, the properties of the adsorbent in the canister. In the exemplary diagram 600, the conditions for performing a variable vacuum diagnostic may include, for example, a scenario where the ambient temperature is 65°F and the canister state of charge is 20% saturated. As discussed herein, situations where the canister state of charge and the ambient temperature are such that undesirable charging of the canister may occur may be understood to include situations where the canister state of charge and the ambient temperature are above a "combined threshold." Additionally, with reference to Figure 6It will be appreciated that the variable vacuum target may be less negative (decreased) relative to atmospheric pressure based on lower canister state of charge and lower fuel volatility, and may be more negative (increased) relative to atmospheric pressure based on higher canister state of charge and higher fuel volatility.

[0090] Therefore, returning to 430 , if the conditions for performing a variable vacuum diagnostic are indicated, method 400 may proceed to 435 . At 435 , method 400 may include scheduling a controller wakeup time. In one example, the controller may be scheduled to wake up one or more hours after the key-off event. For example, the controller may be scheduled to wake up after 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, or more than 5 hours. By scheduling the wakeup time one or more hours after the key-off event, it will be appreciated that conditions in the fuel system and / or evaporative emissions system may be allowed to stabilize. Scheduling the wakeup time at 440 may include, for example, setting a timer, wherein upon expiration of the timer, the controller is triggered into a wakeup state.

[0091] In the event that a wakeup time is scheduled at 435, method 400 may proceed to 440. At 440, method 400 may include putting the controller to sleep. At 445, method 400 may include indicating whether the wakeup timer has elapsed, and if not, the controller may remain in a sleep state to conserve battery power. However, in response to the wakeup timer expiring, method 400 may proceed to 450. At 450, method 400 may include: Figure 5 The variable vacuum diagnostic is performed. Method 400 may then end.

[0092] Returning to 430 , in response to indicating that the conditions for performing the variable vacuum diagnostic are not met, method 400 may proceed to 455 . At 455 , method 400 may include scheduling a controller wakeup, similar to that discussed above at 435 . In one example, the wakeup time may be the same as that described at 435 , but in other examples, the wakeup time may be different. For example, the wakeup time may include one or more hours from the key-off event and may include setting a timer as discussed at 435 . By scheduling the controller wakeup one or more hours after the key-off event, it will be appreciated that conditions in the fuel system and / or evaporative emissions system may be allowed to stabilize. For example, as discussed above, for a sealed fuel tank, if the fuel tank maintains a pressure or vacuum greater than a threshold, this may indicate that the fuel tank is free of undesirable evaporative emissions. However, when the vehicle is in operation (where fuel may be constantly sloshing around), pressure buildup may always exist in the fuel system, making it possible for even a small source of undesirable evaporative emissions to build up to a level greater than the threshold, which may result in a false positive result. Similarly, if such a test is performed just after the key is turned off, there may be exhaust heat from the engine, fuel sloshing due to an emergency stop, etc., which may cause pressure buildup in the fuel system, which may complicate any analysis of whether the fuel system is truly free of undesirable evaporative emissions. Therefore, by allowing the vehicle system to stabilize, such issues can be avoided.

[0093] Thus, if the timer is set at 455, method 400 may proceed to 460. At 460, method 400 may include putting the controller to sleep. Proceeding to 465, method 400 may include indicating whether the wakeup timer has elapsed. If not, the controller may continue to remain in the sleep state. However, in response to the wakeup timer expiring at 465, method 400 may proceed to 470 and may include: Figure 7 Population-based fuel system diagnostics are performed. Method 400 may then end.

[0094] Now turn Figure 5 , shows a high-level flow chart for performing variable vacuum based diagnostics for unwanted evaporative emissions from a vehicle's fuel system and / or evaporative emissions system. Specifically, method 500 may constitute the above Figure 4Method 500 is a sub-method of method 400 depicted herein. However, in some examples, method 500 may be used independently and need not be a sub-method of method 400. Method 500 may include first determining the presence or absence of severe and non-severe evaporative emissions in the evaporative emissions system, and then determining the presence or absence of severe and non-severe evaporative emissions in the fuel system. This method may include applying a first negative pressure or vacuum to the evaporative emissions system to diagnose the evaporative emissions system, and may include applying a second negative pressure or vacuum to the fuel system to diagnose the fuel system. In some examples, the first vacuum and the second vacuum may be the same, but in other examples, the first vacuum and the second vacuum may be different. For example, the first vacuum may be less than the second vacuum. In another example, the first vacuum may include a vacuum that is independent of the charge state of the fuel vapor canister and independent of the ambient temperature, while the second vacuum may be a function of the charge state of the canister and may also be a function of the ambient temperature or the fuel temperature.

[0095] Will refer to Figures 1 to 2 Method 500 is described with reference to the system described in

[0045] , but it should be understood that method 500 may be applied to other systems without departing from the scope of this disclosure. Method 500 may be implemented by a controller, such as controller 212, and may be stored as executable instructions in a non-transitory memory. Instructions for implementing method 500 and the remaining methods included herein may be executed by the controller based on instructions stored on the controller's memory and in conjunction with signals received from sensors of the vehicle system, such as the sensors described above with reference to

[0046] Figures 1 to 2 The controller may employ fuel system and evaporative emission system actuators, such as the FTIV (eg, 252 ), vacuum pump (eg, 289 ), CVV (eg, 297 ), CPV (eg, 261 ), etc., according to the methods described below.

[0096] Method 500 begins at 503 and may include sealing the fuel system or maintaining its seal, and may include closing the CVV. For example, the controller may send a signal to the CVV to actuate it closed. Proceeding to 506, method 500 may include purging the evaporative emissions system (e.g., 251) for a predetermined duration. More specifically, vacuum pump 289 may be actuated on to apply vacuum to the evaporative emissions system, but the fuel system is not purged due to the closed FTIV. In one example, purging the evaporative emissions system may include pumping the pressure down to a predetermined negative pressure, such as -8 InH2O. This example is intended to be illustrative, and other predetermined negative pressures may be used. The predetermined negative pressure may be independent of the canister's charge state and ambient temperature, as vacuum applied to the evaporative emissions system may not further charge the canister if the fuel tank is closed. Furthermore, when the applied vacuum is relieved, fresh air may be drawn into the canister, thereby drawing back into the canister any hydrocarbons drawn from the canister to the atmosphere during purging of the evaporative emissions system. In this way, evaporative emission system emptying may be independent of canister loading status and ambient temperature.

[0097] If the vacuum pump is activated to evacuate the evaporative emissions system, method 500 may proceed to 509 . At 509 , method 500 may include indicating whether a threshold vacuum or predetermined negative pressure has been reached. For example, pressure in the evaporative emissions system may be monitored via pressure sensor 282 . If the threshold vacuum has not been reached at 509 , method 500 may proceed to 512 , where an indication may be given as to whether a predetermined duration has elapsed. Specifically, the predetermined duration may include the amount of time it is expected that the threshold negative pressure in the evaporative emissions system will be reached in the absence of significant undesirable evaporative emissions. If the predetermined duration has not elapsed at 512 , the vacuum pump may continue evacuating the evaporative emissions system. However, if the predetermined duration is indicated to have elapsed at 512 , method 500 may proceed to 515 . At 515 , method 500 may include indicating the presence of significant undesirable evaporative emissions originating from the evaporative emissions system. In some examples, significant undesirable evaporative emissions may include undesirable evaporative emissions originating from a source greater than 0.04 inches. In other words, the inability of the vacuum pump to draw the pressure in the evaporative emissions system down to a predetermined or threshold negative pressure may indicate the presence of severe, undesirable evaporative emissions.

[0098] Therefore, method 500 may proceed to 518. At 518, method 500 may include aborting the variable vacuum based test diagnostic. In other words, because of the indication of the presence of severe, undesirable evaporative emissions originating from the evaporative emissions system, it may be undesirable to perform variable vacuum based diagnostics on the fuel system because any vacuum applied to the fuel system may not be pulled down to a desired negative pressure due to the presence of severe, undesirable evaporative emissions in the evaporative emissions system.

[0099] Proceeding to 521, method 500 may include: updating the vehicle operating conditions to reflect the indication of severe undesirable evaporative emissions, and may also include: scheduling a subsequent test of the fuel system diagnostic. For example, a malfunction indicator light (MIL) may be illuminated on the vehicle instrument panel to alert the vehicle driver of the request for vehicle maintenance. In addition, the canister cleaning schedule may be updated to clean the canister frequently to avoid releasing undesirable evaporative emissions into the atmosphere. In some examples, the vehicle may be operated in electric mode as frequently as possible to minimize fuel use, which may prevent refueling events that could otherwise potentially direct fuel tank vapors to the atmosphere. In addition, since the fuel system cannot be diagnosed, a subsequent test of the fuel system diagnostic may be scheduled. For example, a group-based fuel system diagnostic may be scheduled (see Figure 7 ), or the fuel system may be diagnosed under conditions of stagnant pressure or vacuum in the fuel system. Method 500 may then end.

[0100] Returning to 509, in response to reaching the threshold vacuum during purging of the evaporative emissions system, method 500 may proceed to 524. At 524, method 500 may include indicating that there are no significant, undesirable evaporative emissions, and may also include ceasing purging of the evaporative emissions system. In other words, the vacuum pump may be deactivated or turned off. With the vacuum pump turned off, it will be appreciated that CV1 (e.g., 292) and CV2 (e.g., 293) may be closed, and thus, with the CVV closed (and the CPV closed), the evaporative emissions system may be sealed from the atmosphere and the engine intake.

[0101] With the evaporative emissions system sealed from the atmosphere, method 500 may proceed to 527. At 527, method 500 may include indicating whether the pressure loss in the evaporative emissions system is greater than a threshold loss, or whether the rate of pressure loss is greater than a pressure loss rate threshold. If so, method 500 may proceed to 530 and may include indicating the presence of minor undesirable evaporative emissions originating from the evaporative emissions system. Alternatively, if the answer at 527 is no, method 500 may proceed to 533 and may include indicating the absence of minor undesirable evaporative emissions. Minor undesirable evaporative emissions may include, for example, undesirable evaporative emissions originating from sources of 0.02 inches or less. In either case, method 500 may proceed to 536 and may include updating vehicle operating conditions based on the results of the pressure loss test. For example, if minor undesirable evaporative emissions are indicated, the MIL may be illuminated on the vehicle dashboard to alert the vehicle driver of a need for vehicle service. The vehicle may be operated in electric-only mode as frequently as possible to avoid situations (e.g., refueling events) where fuel vapor may be undesirably released to the atmosphere. The canister purge schedule may be updated to reflect the presence of less severe, undesirable evaporative emissions. For example, purge operations may be performed more frequently or more quickly after refueling events to reduce the potential release of undesirable evaporative emissions into the atmosphere. Alternatively, if an indication that the evaporative emissions system is free of both severe and less severe undesirable evaporative emissions may be stored at the controller, and vehicle operating conditions may be maintained at their current state.

[0102] Even if minor undesirable evaporative emissions are indicated, method 500 may still include performing variable vacuum-based diagnostics, as discussed in detail below. More specifically, because only minor undesirable evaporative emissions are indicated, it may be expected that the vacuum pump will be able to pump the fuel system down to a predetermined negative pressure (wherein the predetermined negative pressure may be variable based on the canister loading state and the ambient and / or fuel temperatures).

[0103] Therefore, proceeding to 539, method 500 may include indicating whether the absolute value of the pressure in the fuel system has exceeded a predetermined threshold. The pressure in the fuel system may be monitored, for example, via a fuel tank pressure transducer (e.g., 291). For example, it may indicate whether the negative pressure in the fuel system is greater (e.g., more negative) than a negative fuel system pressure threshold, or whether the positive pressure in the fuel system is greater (e.g., more positive) than a positive fuel system pressure threshold. For example, the positive and negative pressure thresholds may include thresholds that, if met, may indicate the absence of undesirable evaporative emissions from the fuel system. Therefore, if the pressure in the fuel system is greater than the positive pressure threshold or the negative pressure threshold, method 500 may proceed to 542 and may include indicating the absence of undesirable evaporative emissions from the fuel system. This result may be stored at the controller. In response to this indication, the negative pressure in the evaporative emissions system may be relieved at 545. More specifically, the CVV may be commanded to open by the controller by sending a signal to the CVV to actuate it open. In this manner, the pressure in the evaporative emissions system may be returned to atmospheric pressure.

[0104] Proceeding to 548 , method 500 may include updating the vehicle operating conditions to reflect the passing result. For example, the current vehicle operating conditions may be maintained in response to the passing result. Additionally, the controller may be placed in a sleep state. Method 500 may then end.

[0105] Returning to 539, in response to the pressure in the fuel system not being greater than the positive pressure threshold or the negative pressure threshold, method 500 may proceed to 551. At 551, method 500 may include commanding the FTIV to open via a controller sending a signal to the FTIV to actuate it open. With the FTIV commanded open, the fuel system may be fluidly coupled to the evaporative emissions system.

[0106] Proceeding to 554 , method 500 may include purging the fuel system using a variable vacuum target. The variable vacuum target may be based on a lookup table 600 . More specifically, the variable vacuum target may be a function of ambient temperature and the fuel vapor canister filling state. As discussed, at higher ambient temperatures, fuel volatility may increase, which may complicate the interpretation of the pressure loss portion of the fuel system diagnostic after purging the fuel system to a threshold negative pressure and sealing the fuel system. To avoid such issues, a greater (e.g., more negative) pressure may be applied to the fuel system at higher ambient temperatures. However, when a greater vacuum is applied to the fuel system, the issue becomes charging the fuel vapor canister. In other words, the greater the negative pressure, the greater the likelihood of charging the fuel vapor canister. Therefore, the amount of negative pressure applied for fuel system diagnostic testing may be a function of the current canister filling state, thereby reducing the likelihood of releasing undesirable evaporative emissions into the atmosphere. It will be appreciated that conditions that enable the application of a variable vacuum to the fuel system may include the fuel tank being constructed of steel, allowing a greater negative pressure to be applied to the fuel tank without damaging it.

[0107] Therefore, at 554, the vehicle controller may activate the vacuum pump (e.g., 289) to evacuate the fuel system to a target vacuum, where the target vacuum is determined based on lookup table 600. It will be appreciated that evacuating the fuel system in this manner evacuates the fuel system throughout the entire fuel vapor storage canister. Therefore, proceeding to 557, method 500 may include indicating whether the variable vacuum target has been reached within a predetermined duration. Similar to the discussion above, the predetermined duration may include a duration during which the variable vacuum target can be expected to be reached without significant, undesirable evaporative emissions from the fuel system. If the variable vacuum target has not been reached within the predetermined duration at 557, method 500 may proceed to 560. At 560, method 500 may include indicating the presence of significant, undesirable evaporative emissions from the fuel system. This result may be stored, for example, at the controller. In this case, method 500 may proceed to 563 and may include ceasing evacuation of the fuel system by deactivating the vacuum pump. Furthermore, the CVV may be commanded to open. In this manner, the vacuum applied to the fuel system may be relieved. Proceeding to 566, method 500 may include the controller sending a signal to the FTIV to actuate it closed. Proceeding to 548, method 500 may include updating the vehicle operating conditions to reflect the indication of severe, undesirable evaporative emissions originating from the fuel system. For example, the MIL (Milky Way Light) on the vehicle's instrument panel may be illuminated to alert the vehicle driver of a need for vehicle service. In some examples, because severe, undesirable evaporative emissions originating from the evaporative emission system are not present, but severe, undesirable evaporative emissions originating from the fuel system are present, the FTIV may be commanded to open to preferentially direct fuel tank vapors to the canister rather than potentially allowing fuel vapors to escape to the atmosphere via the source of severe, undesirable evaporative emissions in the fuel system. In other words, by opening the FTIV, fluid flow between the fuel tank and the canister faces less resistance than through the source of severe, undesirable evaporative emissions, allowing fuel vapors to be preferentially directed to the canister rather than to the atmosphere via the source of severe, undesirable evaporative emissions. Furthermore, at 548, the controller may be placed in a sleep state. Method 500 may then end.

[0108] Returning to 557, if the variable vacuum target is achieved within the predetermined duration, method 500 may proceed to 569. At 569, method 500 may include indicating that significant, undesirable evaporative emissions are not present. Furthermore, evacuation of the fuel system may be stopped by commanding the vacuum pump to an off configuration. Proceeding to 572, method 500 may include sealing the fuel system from the atmosphere by commanding the FTIV to close. It will be appreciated that closing the FTIV may occur substantially simultaneously with deactivating the vacuum pump.

[0109] With the fuel system sealed from the atmosphere, method 500 may proceed to 575 and may include indicating whether a pressure loss in the fuel system is greater than a pressure loss threshold, or whether a pressure loss rate is greater than a pressure loss rate threshold. In some examples, the pressure loss threshold and / or the pressure loss rate threshold may be a function of ambient temperature, fuel temperature, and may also be a function of a target variable vacuum level achieved during purging. In other words, the threshold may be adjusted based on a variable vacuum target that is a function of ambient temperature and canister loading status. More specifically, the threshold may be adjusted to provide a greater signal-to-noise ratio as ambient temperature, fuel temperature, fuel volatility, etc. increase. Reference Figure 6 Consider a scenario where the ambient temperature is greater than 90°F. Therefore, the fuel system may be purged to -28 InH2O because, at such high temperatures, a significant pressure loss due to fuel volatility can be expected. Thus, the threshold used to indicate whether the fuel system is free of undesirable evaporative emissions can be adjusted based on the expected or predicted loss due to fuel volatility, which is further a function of ambient temperature, fuel temperature, fuel level, etc. In this way, the signal-to-noise ratio of the test for undesirable evaporative emissions can be increased, thereby reducing false faults due to fuel volatility issues. In other words, when setting the threshold based on the variable vacuum target, the difference between the threshold and the variable vacuum target can increase as the variable vacuum target becomes more negative relative to atmospheric pressure and can decrease as the variable vacuum target becomes less negative relative to atmospheric pressure. As a specific example, if the fuel system is purged to -8 InH2O, the threshold for indicating undesirable evaporative emissions may be set at, for example, -6 InH2O, while if the fuel system is purged to -28 InH2O, the threshold for indicating undesirable evaporative emissions may be set at -18 InH2O to account for expected losses due to fuel volatility at higher temperatures.

[0110] If the answer is no at 575 , method 500 may proceed to 578 and may include indicating that there are no undesirable evaporative emissions originating from the fuel system. In response to this indication, method 500 may proceed to 581 . At 581 , method 500 may include relieving the negative pressure applied to the fuel system. Specifically, at 581 , the CVV and FTIV may be commanded to open, thereby allowing the fuel system to return to atmospheric pressure. Furthermore, by commanding the CVV and FTIV to open, a partial purge of the fuel vapor canister may be performed, as opening the CVV and FTIV draws fresh air through the vent line and through the canister, which may desorb at least a portion of the fuel vapor from the canister into the fuel tank.

[0111] In response to the pressure in the fuel system (and evaporative emissions system) reaching atmospheric pressure, method 500 may proceed to 566. At 566, method 500 may include commanding the FTIV to close via the controller by sending a signal to the FTIV to actuate it closed. Proceeding to 548, method 500 may include updating vehicle operating conditions. Updating vehicle operating conditions at 548 may include indicating the absence of undesirable evaporative emissions in the fuel system and, therefore, may include maintaining current vehicle operating conditions to reflect a passing result. Furthermore, at 548, method 500 may include placing the controller in a sleep state. Method 500 may then end.

[0112] Returning to 575, in response to the pressure in the fuel system being greater than the pressure loss threshold, or in response to the pressure loss rate being greater than the pressure loss rate threshold, method 500 may proceed to 584. At 584, method 500 may include indicating the presence of minor, undesirable evaporative emissions originating from the fuel system. In response to this indication, method 500 may proceed to 581 and may include relieving vacuum in the fuel system (and evaporative emissions system) by commanding the CVV and FTIV to open. As discussed, this action may result in partial purging of fuel vapors stored in the canister back into the fuel tank.

[0113] After the vacuum is relieved (e.g., the pressure in the fuel system and the evaporative emissions system returns to atmospheric pressure), method 500 may proceed to 566 and may include closing the FTIV to seal the fuel system from the atmosphere. Proceeding to 548, method 500 may include updating the vehicle operating conditions. For example, the MIL may be illuminated on the vehicle dashboard to indicate a request for service to the vehicle. Additionally, in some examples, the FTIV may be commanded open so that fuel vapors may be preferentially directed to the fuel vapor canister rather than potentially escaping through less severe sources of undesirable evaporative emissions in the fuel system. In such an example, as a result of commanding the FTIV open, the canister cleaning schedule may be updated so that the canister is cleaned more frequently. At 548, method 500 may include placing the controller in a sleep state. Method 500 may then end.

[0114] Return to Figure 4 As discussed, in response to the conditions for performing a variable vacuum diagnostic not being met, method 400 may continue according to Figure 7 Perform population-based fuel system diagnostics.

[0115] Therefore, turning to Figure 7, illustrates a high-level exemplary method 700 for performing population-based fuel system diagnostics. More specifically, method 700 may include first testing for the presence of unwanted evaporative emissions originating from the evaporative emissions system with the FTIV closed, thereby isolating the fuel system from the evaporative emissions system. Next, a population-based diagnostic may be performed to determine the presence or absence of unwanted evaporative emissions originating from the fuel system. Importantly, this diagnostic may be performed without fluidly coupling the fuel system to the evaporative emissions system, which may prevent further loading of the fuel vapor canister.

[0116] Will refer to Figures 1 to 3 Method 700 is described with reference to the system described in

[0065] , but it should be understood that method 700 may be applied to other systems without departing from the scope of this disclosure. Method 700 may be implemented by a controller, such as controller 212, and may be stored as executable instructions in a non-transitory memory. Instructions for implementing method 700 and the remaining methods included herein may be executed by the controller based on instructions stored on the controller's memory and in conjunction with signals received from sensors of the vehicle system, such as the sensors described above with reference to

[0066] Figures 1 to 3 The controller may employ fuel system and evaporative emission system actuators, such as the FTIV (eg, 252 ), vacuum pump (eg, 289 ), CVV (eg, 297 ), CPV (eg, 261 ), etc., according to the methods described below.

[0117] Method 700 begins at 701 and may include testing for the presence or absence of undesirable evaporative emissions originating from the evaporative emissions system according to steps 503-536 of method 500. Briefly, vacuum may be applied to the evaporative emissions system with the FTIV closed, and the presence or absence of significant undesirable evaporative emissions may be indicated based on whether a threshold vacuum is reached during purging. In response to the absence of significant undesirable evaporative emissions, the evaporative emissions may be sealed from the atmosphere, and the presence or absence of less significant undesirable evaporative emissions may be indicated based on pressure loss in the sealed evaporative emissions system.

[0118] Regardless of whether severe undesirable evaporative emissions are present, less severe undesirable evaporative emissions are present, or neither severe nor less severe undesirable evaporative emissions are present, method 700 may proceed to 703. At 703, method 700 may include relieving the negative pressure in the evaporative emissions system. For example, the CVV may be commanded to open so that the pressure in the evaporative emissions system can return to atmospheric pressure.

[0119] Proceeding to 705, method 700 may include indicating whether the absolute value of the pressure in the sealed (e.g., FTIV closed) fuel system is greater than a predetermined negative pressure (relative to atmospheric pressure) or greater than a predetermined positive pressure (relative to atmospheric pressure). If so, method 700 may proceed to 710 and indicate the absence of undesirable evaporative emissions from the fuel system. Method 700 may then proceed to 715, where the vehicle operating conditions may be updated. For example, in response to indicating the absence of undesirable evaporative emissions from the fuel system, the current vehicle operating conditions may be maintained, and the results of the test may be stored at the controller. Method 700 may then end.

[0120] Returning to 705, in response to the pressure in the fuel system being below a positive pressure threshold or a negative pressure threshold, method 700 may proceed to 720. At 720, method 700 may include: generating the above Figure 3The vehicle group or selected vehicle group discussed above. In some examples, the vehicle group may be referred to as a plurality of vehicles, a group of vehicles, a set of vehicles, etc. To generate or select a vehicle group from which a vehicle being diagnosed (VD) may retrieve fuel tank pressure data, the following procedure implemented by a controller of the VD may be utilized. For example, the VD may send a wireless request to one or more vehicles within the VD's wireless communication or within a predetermined threshold distance or radius (e.g., 320) thereof. The wireless request may include a request for information from the vehicle, including: data related to the time since the last key-off; engine run time for the most recent previous drive cycle prior to the key-off event; fuel level; vehicle make / model information; whether the vehicle has a sealed fuel tank; fuel tank pressure data, etc. Among the vehicles receiving the wireless request, it may be further determined which of the vehicles are to be retrieved for one or more data sets related to fuel tank pressure. It will be appreciated that the determined vehicles from which to retrieve one or more data sets may include the group, the selected group, the plurality of vehicles, the group of vehicles, the set of vehicles, etc. The group can be selected based on vehicle make / model; for example, only vehicles of a similar make / model to the vehicle being diagnosed can be considered. For example, if the VD includes sedans, large trucks can be excluded from the group. Additionally or alternatively, the group can be selected based on whether one or more vehicles have a fuel tank that is normally sealed except for events such as refueling or performing diagnostic tests. For example, vehicles that do not have a sealed fuel tank can be excluded from the group. Additionally or alternatively, the group can be selected based on whether one or more vehicles have a fuel level within a predetermined fuel level range. As an example, the group can be selected based on whether the fuel level of one or more vehicles is within a threshold fuel level (e.g., within 5% or within 10%) of the fuel level indicated for the VD. Vehicles that do not have a fuel level within the threshold fuel level indicated for the VD can be excluded from the group. Additionally or alternatively, the group can be selected based on the time since key-off (e.g., the time since key-off is greater than a threshold key-off duration). The threshold key-off duration may include a duration during which any exhaust heat from the engine from the previous drive cycle no longer contributes to the generation of fuel vapor in the fuel tank or no longer affects the fuel tank temperature. For example, vehicles that have not been shut down for the threshold key-off duration may be excluded from the group.

[0121] In the event that the vehicles constituting the group have been selected via the VD controller processing the wireless request, method 700 may proceed to 725. At 725, method 700 may include retrieving one or more data sets including fuel tank pressure from the vehicles constituting the group. Retrieving one or more data sets including fuel tank pressure and / or one or more data sets including fuel level may be performed via wireless communication between the VD controller and one or more controllers of the vehicles constituting the group. As described above with respect to Figure 3 As discussed, in some examples, data including fuel tank pressure data may be retrieved within a predetermined time period.

[0122] In response to retrieving fuel tank pressure data from the vehicles comprising the group, method 700 may proceed to 730. At 730, method 700 may include processing the data retrieved from the group. As discussed above, in some examples, the data including fuel tank pressure may be processed to determine average fuel tank pressure data for each vehicle, and further processed to determine an average total fuel tank pressure from all vehicles comprising the group within a predetermined time period for which the data was retrieved. Similarly, an average fuel tank pressure of the VD may be determined.

[0123] Having processed the data retrieved from the swarm at 730 and having processed the data from the VD, method 700 may further include the VD controller comparing the processed fuel tank pressure data from the VD with the processed fuel tank pressure data from the swarm.

[0124] Proceeding to 735, method 700 may include indicating whether the retrieved data correlates with data obtained from the VD. As discussed above, correlation of the fuel tank pressure data from the VD with the fuel tank pressure data from the population may include the fuel tank pressure data from the VD being within a certain threshold (e.g., within 5% or less) of the fuel tank pressure data from the population.

[0125] If the data is indicated as correlated at 735, method 700 may proceed to 745 and may include indicating that there are no undesirable evaporative emissions originating from the fuel system. In other words, by performing fuel system diagnostics based on population data as discussed, in the event that the fuel tank pressure in the sealed fuel tank is not experiencing a pressure greater than a positive or negative pressure threshold (see step 705 of method 700), the fuel system may still be diagnosed as to whether the fuel system is likely to have a source of undesirable evaporative emissions. In the event that the data is correlated at 735, it can be understood that the fuel systems comprising the population, on average, are not experiencing a pressure buildup (positive or negative) greater than a positive or negative pressure threshold. In other words, because the data is correlated, the vehicles (both VD and population) are likely experiencing a portion of a diurnal cycle in which the pressure in the fuel system of such vehicles is close to atmospheric pressure.

[0126] In response to the indication of the absence of fuel tank degradation, method 700 may proceed to 750 and may include updating vehicle operating conditions. Updating vehicle operating conditions at 750 may include recording a result, including an indication of the absence of undesirable evaporative emissions from the VD's fuel system, at the VD controller (e.g., 212). Furthermore, updating vehicle operating conditions at 750 may include maintaining the current evaporative emissions testing schedule, maintaining the current fuel vapor canister purge schedule, maintaining current engine operating conditions (at the next key-on event), etc. In other words, the fuel system is likely to undergo another test for the presence or absence of undesirable evaporative emissions shortly after such an indication. Therefore, if the pressure in the VD's fuel system is likely not greater than a positive pressure threshold or a negative pressure threshold due to the presence of undesirable evaporative emissions, another diagnostic test may be performed on the fuel system within a short period of time. Furthermore, in some examples, at 750, method 700 may include placing the controller in a sleep state. Method 700 may then end.

[0127] Returning to 735, in response to an indication that the fuel tank pressure data from the VD does not correlate with the data retrieved from the population, method 700 may proceed to 740 and may include indicating the presence of undesirable evaporative emissions originating from the VD's fuel system. Such indication may include setting a flag at a controller of the VD and may also include illuminating a malfunction indicator light (MIL) on an instrument panel of the VD to alert the vehicle driver of the need for vehicle service.

[0128] Proceeding to 750, method 700 may include updating the vehicle operating conditions in response to an indication of the presence of unwanted evaporative emissions from the fuel system. In one example, updating the vehicle operating conditions may include taking mitigating action in response to an indication of the presence of unwanted evaporative emissions from the fuel system from the VD. In some examples, taking mitigating action may include commanding the FTIV (e.g., 252) to open. By commanding the FTIV to open, fuel tank vapors may be preferentially directed to the fuel vapor canister rather than the atmosphere, as discussed above. Taking mitigating action may also include updating the canister cleaning schedule to clean the canister more frequently when the FTIV is commanded to open. It will be understood that when the FTIV is commanded to open, the CVV (e.g., 297) may also be commanded to open (if not already open). Additionally, at 750, in some examples, method 700 may include placing the controller in a sleep state. Method 700 may then end.

[0129] So, about Figures 5 to 7The described method may implement a method comprising: evacuating a fuel tank located in a vehicle's fuel system to a variable vacuum target based on fuel volatility in the tank and a charge state of a fuel vapor storage canister configured to capture and store fuel vapor from the fuel tank to test for the presence or absence of undesirable evaporative emissions from the fuel system. In one example of this method, the fuel tank may comprise a steel fuel tank. Furthermore, the fuel volatility may be a function of one or more of current and / or forecast ambient temperature, and / or fuel temperature. In some examples, evacuating the fuel system may direct fuel vapor from the fuel tank throughout the fuel vapor storage canister, and evacuating the fuel system is performed via a vacuum pump located in a vacuum pump conduit between the fuel vapor storage canister and atmosphere. The vacuum pump may be located in parallel with a canister vent valve located in a vent line between the fuel vapor storage canister and atmosphere. In such an example, the canister vent valve may be commanded to a closed configuration during evacuation of the vehicle's fuel system to the variable vacuum target.

[0130] As an example of such a method, the variable vacuum target may be decreased based on a lower canister load state and lower fuel volatility, and may be increased based on a higher canister load state and higher fuel volatility. Additionally, such a method may include not purging the fuel system of the vehicle to the variable vacuum target in response to an indication that purging the fuel vapor canister would load the fuel vapor storage canister to an undesirable level or above. In other words, the method may include purging the fuel system to the variable vacuum target only in the event that the fuel vapor canister is loaded below an undesirable level, such that the risk of leaking emissions to the atmosphere is reduced. In the event that an indication is given that purging the fuel system to the variable vacuum target would load the fuel vapor storage canister to an undesirable level or above, an alternative test may be performed for the presence or absence of undesirable evaporative emissions from the fuel system. For example, the alternative test may include a population-based fuel system diagnostic based on fuel tank pressure data from a determined population of vehicles.

[0131] In this method, with the fuel system purged to the variable vacuum target, the fuel system may be sealed in response to achieving the variable vacuum target, and the presence of non-severe undesirable evaporative emissions from the fuel system may be indicated in response to pressure in the fuel system reaching or exceeding a pressure loss threshold within a predetermined duration after sealing the fuel system, and / or in response to pressure in the fuel system increasing at a loss rate greater than a pressure loss rate threshold within the predetermined duration.

[0132] The above about Figures 5 to 7 The described method may additionally implement a method comprising: operating a vehicle in a first mode to evacuate the fuel system to a variable vacuum level to perform a first test for undesirable evaporative emissions originating from the fuel system under a first operating condition in which a charge state of a fuel vapor storage canister configured to capture and store fuel vapor from a fuel system, in combination with an ambient temperature, is below a combined threshold; and operating the vehicle in a second mode to perform a second test for undesirable evaporative emissions that does not include evacuating the fuel system to the variable vacuum level, in a second operating condition in which the charge state of the fuel vapor storage canister, in combination with the ambient temperature, is above the combined threshold.

[0133] As one example, operating the vehicle in both the first mode and the second mode may occur during a key-off state of the vehicle.

[0134] In this example, operating the vehicle in the first mode may include evacuating the fuel system through the entire fuel vapor storage canister via a vacuum pump positioned in a vacuum pump conduit between the fuel vapor storage canister and atmosphere, wherein the vacuum pump is coupled in parallel with a canister vent valve positioned in a vent line between the fuel vapor storage canister and atmosphere. In this example, the canister vent valve may be commanded to close prior to operating the vehicle in the first mode to evacuate the fuel system to the variable vacuum level.

[0135] In another example of the method, operating the vehicle in the first mode may further include indicating an absence of significant undesirable evaporative emissions from the fuel system in response to pressure in the fuel system reaching or exceeding the variable vacuum level, then deactivating the vacuum pump and sealing the fuel system. With the fuel system sealed, the presence of non-severe undesirable evaporative emissions may be indicated in response to a pressure loss in the fuel system being greater than a pressure loss threshold and / or in response to a pressure loss rate being greater than a pressure loss rate threshold within a predetermined duration after sealing the fuel system.

[0136] In another example of this method, operating the vehicle in the second mode may include arranging to awaken a controller of the vehicle to perform the second test for undesirable evaporative emissions, wherein the second test includes indicating whether an absolute value of pressure in the fuel system of the vehicle is greater than a threshold, and if not, performing a population-based fuel system diagnostic. Such a population-based diagnostic may involve retrieving fuel tank pressure data from a population of vehicles within a predetermined distance of the vehicle; comparing the fuel tank pressure data from the population of vehicles with fuel tank pressure data from the vehicle; and, in response to the fuel tank pressure data from the population of vehicles not correlating with the fuel tank pressure data from the vehicle, indicating undesirable evaporative emissions originating from the fuel system of the vehicle.

[0137] Furthermore, it will be appreciated that operating the vehicle in the second mode may not further charge the fuel vapor storage canister.

[0138] As discussed above, in some examples, there may be an opportunity to test the fuel system and / or evaporative emissions system for evaporative emissions by monitoring pressure changes in the fuel system and / or evaporative emissions system after a key-off event. This test may include an EONV test, but many factors can influence the results of such a test. Specifically, the robustness of the EONV test can be based on the exhaust heat from the engine during the drive cycle immediately prior to key-off, the aggressiveness of the drive cycle, the ambient temperature, and ambient weather conditions (e.g., wind, rain, humidity, etc.). Furthermore, such a test may include a predetermined duration (e.g., 45 minutes). Therefore, while there may be an opportunity to perform such a test, there may be circumstances where it may not be desirable to do so. One example may include a scenario where it is desirable to test the fuel system and / or evaporative emissions system for the presence or absence of undesirable evaporative emissions, but where it is likely that the vehicle may be restarted before the test is complete (e.g., restarted in less than 45 minutes). For example, if the vehicle controller is able to learn common routes traveled by the vehicle, this possibility can be indicated, including how long a particular stop is predicted to last. If the predicted stop is of short duration, it may be desirable to quickly test for the presence or absence of undesirable evaporative emissions. Such a test may include evacuating the fuel system and / or evaporative emissions system just prior to a learned key-off event so that the pressure rise portion of such a test may be performed immediately after the key-off event. Figures 9 and 10 This test is described in detail.

[0139] Therefore, in order to conduct such a test, the vehicle controller may include a method for learning the path that the vehicle normally travels. Figure 8, a high-level exemplary method 800 for learning common driving routes traveled by a vehicle is shown. More specifically, the method 800 can be used to learn common driving routes and can further be used to learn / predict stops and stop durations associated with specific driving routes. It will be understood that "stop" herein can refer to a vehicle shutdown event (e.g., a key-off event). The duration of the learned / predicted stops corresponding to specific driving routes can be stored in one or more lookup tables stored at the vehicle controller. Further, the final destination corresponding to one or more specific learned / predicted driving routes can be determined and stored in one or more lookup tables stored at the vehicle controller. Such information can be used to schedule appropriate evaporative emissions testing diagnostic procedures.

[0140] Reference will be made to the description and Figures 1 to 3 The method 800 is described with respect to the system shown in FIG. 1 , but it should be understood that similar methods may be applied to other systems without departing from the scope of the present disclosure. The method 800 may be performed by a controller such as Figure 2 The instructions for implementing method 800 and the remaining methods included herein may be executed by the controller based on instructions stored on the controller's memory and in conjunction with signals received from sensors of the engine system, such as those described above. Figures 1 to 2 The controller may employ fuel system and evaporative emission system actuators according to the methods described below: canister vent valve (CVV) (eg, 297 ), canister purge valve (CPV) (eg, 261 ), etc.

[0141] Method 800 begins at 805 and may include indicating whether a key-on event is indicated. A key-on event may include using an ignition key to start the vehicle in an engine start mode or a pure electric operation mode. In other examples, the key-on event may include pressing an ignition button on, for example, a dashboard. Other examples may include a key fob (or other remote device, including a smartphone, tablet, etc.) starting the vehicle in an engine start mode or a pure electric operation mode. If a key-on event is not indicated at 805, method 800 may proceed to 810 and may include maintaining current vehicle operating parameters. For example, at 810, method 800 may include maintaining the CPV, CVV, FTIV, engine, etc. in their current configuration and or current operating mode. Method 800 may then end.

[0142] Returning to 805 , in response to indicating a key-on event, method 800 may proceed to 815 and may include accessing vehicle location, driver information, day of the week (DOW), time of day (TOD), etc. The driver's identity may be entered by the driver or inferred based on driving habits, seat position, cabin climate control preferences, voice activation commands, etc. The vehicle location may be accessed via an onboard navigation system (e.g., via GPS) or other means (such as via wireless communication with the Internet).

[0143] Proceeding to 820, method 800 may include recording vehicle route information during a drive cycle beginning with a key-on event. In some examples, the vehicle route information may be divided into one or more segments, where the one or more segments are bounded by a key-on event indicating a starting location and a key-off event indicating a final destination. However, it is understood that one or more stops may occur between the key-on event signaling the start of the route and the key-off event indicating arrival at the final destination. Such stops may provide an opportunity to perform evaporative emissions diagnostic testing, depending on the duration of the stop, as discussed in further detail below.

[0144] At 820, the vehicle controller may continuously collect data regarding the vehicle's operation / condition, location, traffic information, local weather information, and the like from various sensor systems and external sources. The data may be collected by, for example, GPS (e.g., 132), inertial sensors (e.g., 199), lasers, radar, sonar, acoustic sensors, and the like (e.g., 133). Other feedback signals may also be read from the vehicle, such as input from sensors specific to the vehicle. Exemplary sensors may include tire pressure sensors, engine temperature sensors, brake thermal sensors, brake pad status sensors, tire tread sensors, fuel sensors, oil level and quality sensors, and air quality sensors for detecting temperature, humidity, and the like. Furthermore, at 820, the vehicle controller may also retrieve various types of non-real-time data, such as information from detailed maps, which may be stored at the controller or may be retrieved wirelessly.

[0145] Therefore, data about a particular route or trip route may be obtained and stored at the vehicle controller during the process of driving the vehicle along a particular vehicle driving route. Proceeding to 825, method 800 may include: processing the data to establish a predicted / learned driving route. For example, a large number of trip routes and corresponding information may be obtained and stored at the vehicle controller so that the predicted / learned driving route can be implemented with high accuracy. In some examples, the vehicle may travel along a route that is not frequently traveled (e.g., not "commonly used"). Therefore, it will be appreciated that route information that is not significantly related to commonly traveled routes may be periodically forgotten or removed from the vehicle controller in order to prevent the accumulation of excessive data related to the vehicle's driving routine.

[0146] In some examples, data collected from vehicle travel routines (including GPS data) can be applied to one or more machine learning algorithms to determine common vehicle travel routes. This example is intended to be illustrative and not limiting. For example, any common vehicle route learning method can be used by the vehicle controller to establish the learned travel route without departing from the scope of this disclosure.

[0147] Learning the travel route at 825 may include determining stops between the starting destination and the final destination. For example, learning the travel route at 825 may include learning / predicting stops (e.g., vehicle shutdown events) that are typically less than a predetermined duration (e.g., less than 45 minutes), and may also include learning / predicting stops that are typically greater than a predetermined duration (e.g., greater than 45 minutes). As discussed above and discussed in further detail below, this information may be used to schedule an evaporative emissions test diagnostic.

[0148] Proceeding to 830, method 800 may include storing information related to the learned travel route in one or more lookup tables at the vehicle controller. Such information may include segments of the particular vehicle route in which stops were indicated, and may also include an indication of the learned / predicted duration of each indicated stop. As an example, consider a scenario in which a vehicle operator drives to work each morning but stops at a coffee shop for less than 45 minutes (e.g., up to 20 minutes) to eat breakfast. Such a route may include an opportunity to conduct a quick test (e.g., a test that is expected to be completed more quickly than an EONV test that relies on pressure / vacuum buildup in the fuel system / evaporative emissions system after key-off) for the presence or absence of undesirable evaporative emissions from the fuel system and / or evaporative emissions system. The following will discuss the Figures 9 and 10 The method used to perform this test is discussed in detail.

[0149] Thus, the available Figure 8Such a lookup table generated by the method of

[0014] can be used to schedule an evaporative emissions test diagnostic procedure so that robust results can be achieved. More specifically, a rapid test for the presence or absence of undesirable evaporative emissions originating from the fuel system / evaporative emissions system (also referred to herein as an active purge evaporative emissions test or an active variable vacuum purge evaporative emissions test) can be scheduled for learned stops of less than a predetermined duration (e.g., 45 minutes), which may mitigate or eliminate the risk of prematurely aborting an initiated evaporative emissions test (e.g., failing to complete an EONV test diagnostic).

[0150] Now turn Figure 9 , a high-level flow chart of an exemplary method 900 for scheduling an active variable vacuum evaporative emissions test is shown. More specifically, an active variable vacuum evaporative emissions test may be scheduled for a learned / predicted stop during a learned / predicted drive cycle, where the learned / predicted stop is expected to be less than a predetermined duration (e.g., less than 45 minutes).

[0151] Reference will be made to the description and Figures 1 to 2 The method 900 is described with respect to the system shown in FIG. 1 , but it should be understood that similar methods may be applied to other systems without departing from the scope of the present disclosure. The method 900 may be performed by a controller (such as Figure 2 The instructions for implementing method 900 and the remaining methods included herein may be executed by the controller based on instructions stored on the controller's memory and in conjunction with signals received from sensors of the engine system, such as the sensors referenced above. Figures 1 to 2 The controller may employ fuel system and evaporative emission system actuators according to the methods described below: canister ventilation valve (CVV) (e.g., 297), canister purge valve (CPV) (e.g., 261), FTIV (e.g., 252), vacuum pump (e.g., 289), etc.

[0152] Method 900 begins at 905 and may include indicating whether a key-on event is indicated. As discussed above, a key-on event may include using an ignition key to start the vehicle in an engine start mode or an electric-only operating mode. In other examples, a key-on event may include pressing an ignition button, such as on a dashboard. Other examples may include a key fob starting the vehicle in an engine start mode or an electric-only operating mode. If a key-on event is not indicated at 905, method 900 may proceed to 910 and may include maintaining current vehicle operating parameters. For example, at 910, method 900 may include maintaining the CPV, CVV, engine, motor, vacuum pump, etc. in their current configuration and or current operating mode. Method 900 may then end.

[0153] Returning to 905, if a key-on event is indicated, method 900 may proceed to 915. At 915, method 900 may include: accessing driving route information. For example, accessing driving route information at 915 may include: retrieving learned driving route information from the vehicle controller. More specifically, a particular learned driving route may be indicated as being the same as the current driving route. In other words, the current driving route may match the learned driving route with a high probability. The learned driving route may be matched to the current driving route based on multiple variables, including vehicle location, time of day, date, day of the week, trajectory and / or driver identity. The driver's identity may be entered by the driver, or may be inferred based on driving habits, seat position, cabin climate control preferences, voice activation commands, etc. In another example, the vehicle operator may enter one or more destinations into the vehicle's navigation system (e.g., GPS), so that accessing driving route information at 915 may include: accessing driving route information entered by the vehicle driver. In some examples, accessing driving route information may include: accessing the route information entered by the vehicle driver. Figure 8 The lookup table generated by the method.

[0154] Proceeding to 920, method 900 may include indicating whether any predicted / learned stops are indicated for the particular travel route comprising the current drive cycle. More specifically, at 920, method 900 may include indicating whether any predicted / learned stops are expected to be less than a predetermined threshold duration, where the predetermined threshold duration may include, for example, a duration of less than 45 minutes. If, at 920, it is indicated that no predicted / learned stops are indicated that are expected to be less than the predetermined threshold duration, method 900 may proceed to 925 and may include continuing the drive cycle without scheduling an active variable vacuum evaporative emissions test. Method 900 may then end.

[0155] Returning to 920, in response to one or more predicted / learned stops including a stop expected to be less than a predetermined duration, method 900 may proceed to 930 and may include scheduling an active variable vacuum purge evaporative emissions test for one or more of the predicted / learned stops. In some examples where more than one predicted / learned stop is indicated to be less than the predetermined duration for the current drive cycle, more than one active purge evaporative emissions test may be scheduled for the more than one predicted / learned stops. Alternatively, in other examples, only one active purge evaporative emissions test may be scheduled for one of the one or more predicted / learned stops during the current drive cycle.

[0156] In response to scheduling one or more active purge variable vacuum evaporative emissions tests, method 900 may proceed to 935 and may include: Figure 10The method described herein performs an actively purged variable vacuum evaporative emissions test. Briefly, the actively purged variable vacuum evaporative emissions test may include: immediately prior to a learned stop of less than a predetermined duration, actively reducing the pressure in the fuel system (and evaporative emissions system) to a level that is a function of at least the ambient temperature (and / or fuel temperature) and, in some examples, the canister load state, such that the fuel system can be sealed upon a key-off event; and monitoring pressure loss for indication of the presence or absence of undesirable evaporative emissions originating from the fuel system. By actively reducing the pressure in the fuel system (and evaporative emissions system) immediately prior to key-off, the pressure loss test can be performed quickly and can be expected to complete within the duration of the learned / predicted stop. In this way, the completion rate of the test for undesirable evaporative emissions can be improved. Method 900 may then terminate.

[0157] Now turn Figure 10 , a high-level flow chart of an exemplary method 1000 for conducting an active variable vacuum evaporative emissions test is shown. More specifically, an active variable vacuum evaporative emissions test may be scheduled for one or more stops during a driving route, where the one or more stops are predicted to be less than a predetermined threshold duration (e.g., less than 45 minutes).

[0158] Reference will be made to the description and Figures 1 to 2 The method 1000 is described with respect to the system shown in FIG. 1 , but it should be understood that similar methods may be applied to other systems without departing from the scope of the present disclosure. The method 1000 may be performed by a controller (such as Figure 2 The instructions for implementing method 1000 and the remaining methods included herein may be executed by the controller based on the instructions stored on the controller's memory and in conjunction with signals received from sensors of the engine system, such as the sensors described above. Figures 1 to 2 The controller may employ fuel system and evaporative emission system actuators according to the methods described below: canister ventilation valve (CVV) (e.g., 297), canister purge valve (CPV) (e.g., 261), FTIV (e.g., 252), vacuum pump (e.g., 289), etc.

[0159] Method 1000 begins at 1005 and may include indicating whether conditions for conducting an active variable vacuum evaporative emissions test are met. For example, conditions for conducting an active variable vacuum evaporative emissions test at 1005 may include an indication that the vehicle is within a predetermined threshold time range (e.g., less than 5 minutes) of arriving at a learned / predicted stop, where the learned / predicted stop may include a stop expected to have a duration less than a predetermined duration (e.g., less than 45 minutes). This indication may be provided to a vehicle controller (e.g., 212) via an onboard navigation system (GPS), via a learned travel route stored at the controller in a lookup table, or the like. Conditions for conducting an active variable vacuum evaporative emissions test may also include an indication that the engine is not operating. If the engine is not operating, it will be appreciated that the active variable vacuum test may include depressurizing (purging) the fuel system and the evaporative emissions system via a vacuum pump (e.g., 289). Therefore, when the engine is not operating, the active purge variable vacuum test can be based on ambient temperature and canister load, as discussed above, because the vacuum pump can draw fuel vapor from the fuel tank into the canister for the test. However, in some examples, the conditions for performing the active purge variable vacuum test may include the engine being in operation. If the engine is in operation, it will be understood that the active purge evaporative emissions test can be based on ambient temperature, rather than canister load. More specifically, because the engine is in operation, the engine intake manifold vacuum can be used to evacuate the fuel system and evaporative emissions system, rather than the vacuum pump. Therefore, for conditions to be met in an engine-operating scenario, the intake manifold vacuum can be greater than a threshold vacuum. Therefore, when the engine is in operation, fuel vapor from the fuel tank can be directed to the engine intake for combustion, rather than being stored in the canister. Thus, if the engine is in operation, the active purge variable vacuum test can be based on ambient temperature, rather than canister load (because, in this approach, the canister is not loaded).

[0160] In some examples, an active purge test may be performed via a vacuum pump in situations where a test for undesirable emissions is requested and the combination of indicated fuel volatility and canister loading is below a combined threshold. Alternatively, if the indicated fuel volatility and canister loading are above the combined threshold, it may be desirable to purge the fuel system using engine vacuum to avoid undesirably loading the canister to a point where blowdown emissions may occur. Therefore, in scenarios where engine vacuum is required, in one example, the engine may be enabled to combust air and fuel while the engine is not already combusting air and fuel. However, there may also be examples where fuel economy may be improved by purging the fuel system by spinning the engine dry via an electric motor or motor. However, such examples may rely on an indication that the temperature of the exhaust catalyst (e.g., 270 ) is greater than a threshold temperature (e.g., a light-off temperature). In situations where spinning the engine dry is desired, an electric heater coupled to the exhaust catalyst (if present) may be enabled to bring the temperature of the exhaust catalyst to a threshold temperature.

[0161] Satisfying the conditions for performing an active purge variable vacuum test may also include an indication that the evaporative emissions system is free of severe and / or non-severe undesirable evaporative emissions. Specifically, while not explicitly illustrated, it is understood that steps 503-536 may be performed at any time while the vehicle is in operation and propulsion is solely electric. This test may be performed while the vehicle is in operation because, in situations where the evaporative emissions system is purged with the fuel tank isolated from the evaporative emissions system (e.g., with the FTIV closed), vapors from the fuel tank are not directed to the fuel vapor canister. Therefore, in situations where the fuel system is isolated from the evaporative emissions system, complications associated with pressure loss due to the presence of fuel vapor / fuel volatility are not an issue. Therefore, it is understood that there may be ample opportunity to test for the presence or absence of undesirable evaporative emissions (both severe and non-severe) originating from the evaporative emissions system. If such a test is performed and the evaporative emissions system indicates the absence of undesirable evaporative emissions, then such a test may not need to be performed again for a predetermined duration, during which time it can be inferred that the evaporative emissions system is free of undesirable evaporative emissions. Thus, in situations where the evaporative emissions system is known to be free of undesirable evaporative emissions, the actively purged variable vacuum test may include indicating the presence or absence of undesirable evaporative emissions originating from the fuel system (because the evaporative emissions system is known to be free of undesirable evaporative emissions), as will be discussed in detail below.

[0162] In a scenario where the engine is off, indicating whether conditions are met for conducting an active purge variable vacuum evaporative emissions test may involve the controller querying the above Figure 6Lookup table 600 is depicted to determine whether an active purge variable vacuum test can be performed based on ambient temperature and canister loading status. If the conditions for an active purge variable vacuum test relying on the vacuum pump during an engine-off state (e.g., canister load and fuel volatility above a combined threshold) are not met based on the canister loading status and ambient temperature, then in some examples, the engine may be powered up or enabled (e.g., turned on to combust air and fuel) so that an active purge variable vacuum test can be performed.

[0163] In some examples, the satisfied condition may include an indication of a desire to evacuate the fuel system to a variable vacuum that is dependent on fuel volatility or fuel volatility and canister load status. Such an example may be indicated via V2X communication between similarly located vehicles while the vehicle is in operation. In other words, the vehicle may send a signal to other vehicles within a predetermined distance of the vehicle to obtain information related to fuel tank pressure data and test diagnostics that are performed within a predetermined timeframe of the request for such information (e.g., within 4 hours or less, 2 hours or less, 1 hour or less, etc.). If the fuel tank pressure data and / or data related to the test diagnostics indicate that a deeper vacuum is required to obtain robust results, then the condition for performing an active evacuation variable vacuum test may be indicated as satisfied.

[0164] If conditions for performing an active purge variable vacuum evaporative emissions test are not indicated at 1005 , method 1000 may proceed to 1010 and may include maintaining current vehicle operating parameters. For example, maintaining current vehicle operating parameters may include maintaining the CPV, CVV, FTIV, vacuum pump (e.g., 289 ), etc., at their current operating states. Furthermore, maintaining current vehicle operating parameters may include, for example, maintaining engine status at its current operating state.

[0165] Method 1000 may then end.

[0166] Alternatively, in response to conditions being met to perform an actively purged variable vacuum evaporative emissions test at 1005, method 1000 may proceed to 1015. At 1015, method 1000 may include commanding the CVV to close to seal the fuel system and the evaporative emissions system from the atmosphere. In response to sealing the fuel system and the evaporative emissions system from the atmosphere by commanding the CVV to close at 1015, method 1000 may proceed to 1020. At 1020, one of two approaches may be taken to evacuate the fuel system and the evaporative emissions system to a variable vacuum level. In a first approach, in which the engine is shut down, evacuating the fuel system may include commanding the FTIV to open (and commanding or maintaining the CPV closed), and querying the controller via the FTIV. Figure 6The lookup table 600 depicted therein, operates a vacuum pump (e.g., 289) to evacuate the fuel system (and evaporative emissions system) based on ambient temperature and canister loading status (in some examples, fuel temperature may be used in addition or alternatively). In other words, in a first approach, evacuating the fuel system (and evaporative emissions system) may include evacuating the fuel system (and evaporative emissions system) to a variable vacuum based on canister loading and ambient temperature. Alternatively, in a second approach in which the engine is in operation, method 1000 may include commanding the FTIV to open, and may also include cycling the CPV to enable vacuum from the intake manifold to be delivered to the fuel system (and evaporative emissions system). The CPV may be cycled based on the vacuum level desired to be applied to the fuel system. Specifically, as discussed, with the engine in operation, the desired vacuum level or target vacuum may be a function of the ambient temperature. Therefore, with the engine in operation, the controller may query Figure 11 A lookup table 1100 is depicted to determine the target vacuum based on the indicated ambient temperature.

[0167] Regardless of whether the fuel system (and evaporative emissions system) is purged via a vacuum pump or via engine intake manifold vacuum at 1020, method 1000 may proceed to 1025. At 1025, method 1000 may include indicating whether a target vacuum (e.g., a target negative pressure relative to atmospheric pressure) has been achieved. This indication may be provided via a fuel tank pressure transducer (e.g., 291) or other pressure sensor (e.g., 282). If the target vacuum has not been achieved, method 1000 may proceed to 1030. At 1030, method 1000 may include indicating whether a predetermined duration has elapsed. For example, the predetermined duration may include a duration during which the target vacuum is expected to be achieved without significant, undesirable evaporative emissions. If, at 1030, it is indicated that the predetermined duration has not elapsed, method 1000 may continue purging the fuel system (and evaporative emissions system). Alternatively, if, at 1030, it is indicated that the predetermined duration has elapsed, method 1000 may proceed to 1035. At 1035, method 1000 may include indicating the presence of significant, undesirable evaporative emissions originating from the fuel system and / or the evaporative emissions system. For example, a flag may be set at the controller, and the MIL (Milky Way Display) may be illuminated on the vehicle's instrument panel to alert the vehicle driver of a need for vehicle service. Proceeding to 1040, method 1000 may include updating vehicle operating parameters in response to the indication of significant, undesirable evaporative emissions. For example, as discussed above, the vehicle may be operated in electric-only mode as frequently as possible, the canister purge schedule may be updated to more frequently purge vapors, and so on. Method 1000 may then end.

[0168] Returning to 1025, in response to reaching the target vacuum, method 1000 may proceed to 1045 and may include maintaining the target vacuum until a key-off event is indicated. Furthermore, although not explicitly shown, in response to reaching the target vacuum at 1025, it may be indicated that there are no significant, undesirable evaporative emissions from the fuel system (and evaporative emissions system). At 1045, if the engine is operating, the CPV may be controlled to a duty cycle that maintains the target vacuum. If the engine is not operating and the fuel system and evaporative emissions system are being evacuated via the vacuum pump, the vacuum pump may be controlled via a controller to maintain the target vacuum. Therefore, proceeding to 1050, method 1000 may include indicating whether a key-off event has occurred. If a key-off event has not been indicated, method 1000 may continue to maintain the target vacuum. Alternatively, in response to indicating a key-off event, method 1000 may proceed to 1055. At 1055, method 1000 may include ceasing evacuation of the fuel system (and evaporative emissions system) and sealing the fuel system from the atmosphere. If the fuel system (and evaporative emissions system) are purged via the engine, step 1055 may include the controller commanding the CPV to close upon a key event and performing an engine shutdown. Alternatively, if the fuel system and evaporative emissions system are purged via a vacuum pump, step 1055 may include the controller commanding the vacuum pump to shut off and maintaining the CVV and CPV closed. In either case, the controller may command the FTIV to close to isolate the fuel system from the atmosphere and the evaporative emissions system.

[0169] It will be appreciated that by isolating the fuel system from the evaporative emissions system, the evaporative emissions system is therefore sealed while the target vacuum exists in the evaporative emissions system with the CVV closed. As discussed, method 1000 may be implemented in response to conditions being met for performing an active purge variable vacuum test, which may include an indication that the evaporative emissions system is emitting no undesirable evaporative emissions (serious and / or non-serious). Therefore, in response to isolating the evaporative emissions system from the fuel system at 1055 , a pressure loss test may not be performed. However, via the closed CVV, closed FTIV, and closed CPV, the evaporative emissions system can remain sealed from the fuel system, the atmosphere, and the engine intake. By maintaining a sealed evaporative emissions system, after performing diagnostics on the fuel system, the FTIV and CVV can be opened simultaneously, or the FTIV can be opened just before the CVV, so that negative pressure in the fuel and evaporative emissions systems can draw fresh air across the fuel vapor canister, which can desorb fuel vapor back into the fuel tank. By implementing the method in this sequence, cross-bleed emissions can be reduced.

[0170] Therefore, proceeding to 1060, in response to the fuel system being decoupled from the evaporative emissions system, method 1000 may include monitoring the fuel system pressure for a predetermined duration. Proceeding to 1065, method 1000 may include indicating whether a pressure loss is greater than a pressure loss threshold and / or whether a pressure loss rate is greater than a pressure loss rate threshold. It will be appreciated that the pressure loss threshold and the pressure loss rate threshold may be a function of ambient temperature, fuel level, or fuel temperature. Furthermore, one or more thresholds may be adjusted based on target vacuum. If, at 1065, the pressure loss is indicated to be not greater than the pressure loss threshold and / or not greater than the pressure loss rate threshold, method 1000 may proceed to 1070. At 1070, method 1000 may include indicating the absence of minor, undesirable evaporative emissions from the fuel system. This result may be stored, for example, by a controller. Proceeding to 1075, method 1000 may include decoupling the fuel system and the evaporative emissions system. Specifically, the CVV may be commanded to open and the FTIV may be commanded to open simultaneously, or in some examples, the FTIV may be commanded to open immediately before the CVV is commanded to open. In this way, fresh air may be drawn across the fuel vapor canister, thereby desorbing fuel vapors in the canister back to the fuel tank, as mentioned above.

[0171] In response to pressure in the fuel system and the evaporative emissions system returning to atmospheric pressure, method 1000 may proceed to 1080 and may include commanding the FTIV to close. With the FTIV closed, method 1000 may proceed to 1085 and may include updating vehicle operating parameters. If the absence of undesirable evaporative emissions is indicated, updating vehicle operating parameters may include maintaining the canister purge schedule, evaporative emissions testing schedule, engine operating conditions, etc., at their current states. Method 1000 may then terminate.

[0172] Alternatively, returning to 1065, in response to the pressure loss being greater than a pressure loss threshold and / or in response to the rate of pressure loss being greater than a pressure loss rate threshold, method 1000 may proceed to 1090. At 1090, method 1000 may include indicating the presence of undesirable evaporative emissions from the fuel system and / or the evaporative emissions system. Such indication may include setting a flag at the controller. Additionally, the MIL may be illuminated on the vehicle's instrument panel to alert the vehicle driver of the need for vehicle service.

[0173] Proceeding to 1075, method 1000 may include: unsealing the fuel system and the evaporative emissions system. For example, as discussed, the CVV and FTIV may be commanded to open simultaneously. Alternatively, in some examples, the FTIV may be commanded to open just before the CVV is opened. In response to the pressure in the fuel system and the evaporative emissions system reaching atmospheric pressure, method 1000 may proceed to 1080 and may include: commanding the FTIV to close. Proceeding to 1085, method 1000 may include: updating vehicle operating parameters. For example, as discussed, in some examples, updating vehicle operating parameters in response to an indication of the presence of undesirable evaporative emissions may include: operating the vehicle in an electric-only operating mode as frequently as possible, updating the canister cleaning schedule to clean the canister more frequently, etc. Method 1000 may then end.

[0174] so, Figures 8 to 11 A method implements a method including, in response to a request to test a fuel system of a vehicle for undesirable evaporative emissions, performing the test in a first operating mode by purging the fuel system through an entire fuel vapor canister configured to capture and store fuel vapor from the fuel system, and performing the test in a second operating mode by purging the fuel system through a portion of the fuel vapor canister. In this example, the method may include purging the fuel system in both the first operating mode and the second operating mode in response to a learned key-off event duration being less than a threshold key-off duration. In one example, both the first operating mode and the second operating mode include purging the fuel system to a variable vacuum level, wherein purging the fuel system to the variable vacuum is determined at least in part based on vehicle-to-vehicle communications indicating that the variable vacuum level is desirable for robustness of the test. In this method, the variable vacuum level in the first operating mode is a function of the fuel vapor canister's state of charge and fuel volatility, and the variable vacuum level in the second operating mode is a function of fuel volatility but independent of the fuel vapor canister's state of charge. In this example, purging the fuel system in the first operating mode is performed via a vacuum pump positioned between the fuel vapor canister and atmosphere, and purging the fuel system in the second operating mode is performed via the engine. In some examples, the method may include, while the vehicle is operating in an electric-only operating mode, activating the engine to combust air and fuel to purge the fuel system in the second operating mode.

[0175] Another example of a method includes: operating a vehicle in a third mode to evacuate a fuel system of the vehicle to a first variable vacuum level for testing for undesirable evaporative emissions from the fuel system during a third operating condition, wherein evacuating the fuel system in the third mode further charges a fuel vapor storage canister with fuel vapor from the fuel system; and operating the vehicle in a fourth mode to evacuate the fuel system of the vehicle to a second variable vacuum level for testing for undesirable evaporative emissions during a fourth operating condition, wherein evacuating the fuel system in the fourth mode prevents further charging of the fuel vapor storage canister with fuel vapor from the fuel system. In this example, the first variable vacuum level is a function of a state of charge of the fuel vapor storage canister and fuel volatility, and the second variable vacuum level is a function of fuel volatility but is independent of the state of charge of the fuel vapor storage canister. In this example, the third operating condition includes the charge state of the fuel vapor storage canister combined with fuel volatility being less than a combined threshold, and the fourth operating condition includes the charge state of the fuel vapor storage canister combined with fuel volatility being greater than the combined threshold. Furthermore, in this method, purging the fuel system in both the third mode and the fourth mode is responsive to a request to perform the test and further responsive to an indication that a learned key-off event has a duration less than a threshold key-off duration. In this method, purging the fuel system in the third mode is performed via a vacuum pump positioned between the fuel vapor canister and atmosphere, and purging the fuel system in the fourth mode is performed via the engine. In some examples, purging the fuel system may be performed while the engine is either burning air and fuel or rotating without fuel via an electric motor.

[0176] Now turn Figure 12, shows an exemplary timeline 1200 for conducting a variable vacuum-based test for undesirable evaporative emissions. Timeline 1200 includes a curve 1205 indicating whether a vacuum pump (e.g., 289) is on or off over time. Timeline 1200 also includes a curve 1210 indicating the state of a CVV (e.g., 297) over time; a curve 1215 indicating the state of a CPV (e.g., 261) over time; and a curve 1220 indicating the state of a FTIV (e.g., 252) over time. In the case of each of curves 1210, 1215, and 1220, the state may include open or closed. Timeline 1200 also includes a curve 1225 indicating the pressure in a vehicle's evaporative emissions system (e.g., 251) as monitored via a pressure sensor (e.g., 282). The pressure may be at atmospheric pressure (atm) or negative (-) relative to atmospheric pressure. Line 1226 represents a threshold vacuum that, if reached during purging the evaporative emissions system, may indicate the absence of significant, undesirable evaporative emissions. Line 1227 represents a threshold pressure that, if reached after the threshold vacuum is reached, may indicate the presence of less significant, undesirable evaporative emissions from the evaporative emissions system. Furthermore, purging the fuel system to the second variable vacuum may also include an indication that the temperature of the exhaust catalyst is greater than a threshold temperature, and if not, the method may further include, if the temperature of the exhaust catalyst is less than the threshold temperature, activating a heating element of the exhaust catalyst to increase the temperature of the exhaust catalyst to greater than the threshold temperature.

[0177] Timeline 1200 also includes a curve 1230, which indicates the pressure in the fuel system (e.g., 218) over time. The pressure can be monitored via a fuel tank pressure transducer (FTPT) (e.g., 291). The pressure in the fuel system can be at atmospheric pressure (atm) or can be negative (-) relative to atmospheric pressure. Timeline 1200 also includes a curve 1235, which represents the fuel vapor canister charge state over time. Over time, the charge state can increase (+) or decrease (-). Timeline 1200 also includes a curve 1240, which indicates the ambient temperature over time. Over time, the ambient temperature can increase (+) or decrease (-). Timeline 1200 also includes a curve 1245, which indicates whether the conditions for performing a variable vacuum (VV) diagnostic for indicating the presence or absence of undesirable evaporative emissions are met (yes) or not met (no) over time. Timeline 1200 also includes a curve 1250, which indicates the presence or absence of unwanted evaporative emissions from the evaporative emissions system over time. Unwanted evaporative emissions can be absent (No), include severe unwanted evaporative emissions (G), or include non-severe unwanted evaporative emissions (NG). Similarly, timeline 1200 also includes a curve 1255, which indicates the presence or absence of unwanted evaporative emissions from the fuel system over time. Timeline 1200 also includes a curve 1260, which indicates the state of a controller of the vehicle over time. Over time, the controller can be awake (Awake) or asleep (Sleep).

[0178] At time t0, although not explicitly shown, it is understood that the vehicle is in a key-off state. The vacuum pump is off (curve 1205), the CVV is open (curve 1210), and both the CPV and FTIV are closed (curves 1215 and 1220, respectively). When the CVV is open, the pressure in the evaporative emissions system approaches atmospheric pressure (curve 1225). Additionally, the pressure in the fuel system approaches atmospheric pressure (curve 1230). Conditions for performing a variable vacuum diagnostic have not been indicated (curve 1245). No undesirable evaporative emissions are indicated in the evaporative emissions system (curve 1250) or the fuel system (curve 1255), and the controller is awake (curve 1260).

[0179] Between time t0 and t1, it is understood that the controller retrieves information related to the ambient temperature and the canister loading status. Figure 6Lookup table 600 depicted at time t1 indicates whether the ambient temperature and canister loading are such that the conditions for performing a variable vacuum diagnostic are met. At time t1, it is indicated that the conditions for performing a variable vacuum diagnostic are met. In other words, it can be understood that the ambient temperature and canister loading conditions are such that the variable vacuum diagnostic can be performed without overloading the fuel vapor canister with fuel vapor. In other words, the ambient temperature and canister loading conditions are such that the variable vacuum diagnostic can be performed without increasing the likelihood of blow-through emissions. Further details of the conditions for performing a variable vacuum diagnostic are discussed above at step 430 of method 400 and will not be repeated here for the sake of brevity.

[0180] If the conditions for performing the variable vacuum diagnostic are met at time t1, it will be appreciated that the variable vacuum diagnostic is scheduled, which may include the controller setting a timer that wakes the controller at the scheduled time after the predetermined duration has elapsed. If the variable vacuum diagnostic is scheduled, at time t2, the controller is placed in a sleep state.

[0181] After the predetermined duration has elapsed, at time t3, the controller returns to wake-up mode. Therefore, the vacuum pump is commanded on, and the CVV is commanded closed. The CVV and FTIV are maintained closed. With the vacuum pump enabled and the FTIV, CPV, and CVV closed, the pressure in the evaporative emissions system becomes negative relative to atmospheric pressure. At time t4, a threshold vacuum (represented by line 1226) is reached, thereby indicating the absence of significant, undesirable evaporative emissions from the evaporative emissions system (curve 1250). It will be appreciated that in exemplary timeline 1200, the threshold vacuum for the evaporative emissions system comprises -8 InH2O. In the absence of significant, undesirable evaporative emissions indicated for the evaporative emissions system, the vacuum pump may be commanded off, which may result in the closure of CV1 (e.g., 292) and CV2 (e.g., 293). In this manner, the evaporative emissions system is sealed from the atmosphere. Between times t4 and t5, pressure loss in the evaporative emissions system is monitored for a predetermined duration, and at time t5, the predetermined duration has elapsed. Because the pressure in the evaporative emissions system has not reached the threshold pressure (represented by line 1227 ), it is indicated that no less severe undesirable evaporative emissions are present in the evaporative emissions system (curve 1250 ).

[0182] At time t5, the FTIV is commanded to open, fluidly coupling the fuel system to the evaporative emissions system. The vacuum pump is reactivated. Because the pressure in the evaporative emissions system is already negative relative to atmospheric pressure, the vacuum pump can evacuate the fuel system using less battery power than if the entire fuel system and evaporative emissions system were evacuated from near atmospheric pressure.

[0183] Based on the predicted ambient temperature and canister loading status, Figure 6 The lookup table 600 depicted at retrieves the negative pressure level (threshold vacuum) to which the fuel system is to be reduced. In this exemplary timeline 1200, it will be appreciated that the threshold vacuum comprises -28 InH2O. Between times t5 and t6, the pressure in the fuel system (and the evaporative emissions system) decreases due to the vacuum pump being activated. The extraction of negative pressure on the fuel system results in the diversion of fuel vapor from the fuel tank to the fuel vapor canister, which causes the fuel vapor canister loading to increase between times t5 and t6. However, due to the specified vacuum level and due to the canister loading level prior to evacuation, this increased canister loading is unlikely to result in undesirable blowdown emissions.

[0184] At time t6, the pressure in the fuel system reaches the threshold variable vacuum (indicated by line 1231). When the threshold variable vacuum is reached, no significant, undesirable evaporative emissions are indicated (curve 1255). If the threshold variable vacuum is reached at time t6, the controller commands the FTIV to close (curve 1220), sealing the fuel system. With the fuel system sealed, pressure loss in the fuel system is monitored between times t6 and t7. Pressure loss is significant between times t6 and t7, but remains below the pressure loss threshold (indicated by curve 1232). More specifically, due to the high ambient temperature, fuel evaporation in the fuel system contributes to pressure loss in the fuel system. However, this contribution to pressure loss does not cause the pressure loss to reach the pressure loss threshold because the fuel tank is evacuated to a level based on ambient temperature to increase the signal-to-noise ratio of the pressure loss portion of the test. Specifically, if the fuel system had only been evacuated to -8 InH2O, fuel evaporation would likely have contributed to increasing the pressure in the fuel system above the pressure loss threshold. However, by evacuating the fuel system to -28 InH2O, the signal-to-noise ratio increases so that fuel evaporation does not cause the pressure loss to increase to the pressure loss threshold.

[0185] Therefore, at time t7, it is indicated that there are no minor, undesirable evaporative emissions originating from the fuel system (curve 1255). With the test complete, the condition for performing the variable vacuum diagnostic is no longer indicated (curve 1245). To relieve pressure in the fuel system and the evaporative emission system, the FTIV and CVV are commanded to open at time t7. Due to the negative pressure in the fuel system and the evaporative emission system, fresh air is drawn through the canister, thereby desorbing a portion or a percentage of the fuel vapor from the storage canister back into the fuel tank between times t7 and t8 (curve 1235). In this way, pressure is relieved between times t7 and t8 (see curves 1225 and 1230). In response to the pressure in the fuel system and the evaporative emission system reaching atmospheric pressure, the controller commands the FTIV to close (curve 1220) to isolate the fuel system from the evaporative emission system. At time t9, the controller is returned to sleep mode.

[0186] While timeline 1200 depicts an example where conditions for performing a variable vacuum diagnostic are indicated to be met, in some examples, conditions for performing a variable vacuum diagnostic may not be indicated to be met. Specifically, there may be ambient temperatures (and / or fuel temperatures) and canister loading conditions that may not result in conditions for performing a variable vacuum diagnostic being met due to an increased likelihood of undesirable blowdown emissions. In such an example, a population-based fuel system diagnostic may be performed, as described above with respect to Figure 4 and Figure 7 Discussed.

[0187] Accordingly, turn Figure 13 , shows an exemplary timeline 1300 for testing for unwanted evaporative emissions from a fuel system based on population data. Timeline 1300 includes a curve 1305 indicating the status of a vacuum pump (e.g., 289) (on or off), and curves 1310 and 1315 indicating the status of the CVV and FTIV, respectively, over time (open or closed). Timeline 1300 also includes a curve 1320 indicating the pressure in the evaporative emissions system as indicated by a pressure sensor (e.g., 282) over time. Line 1321 represents a threshold vacuum that, if reached, may indicate the absence of significant unwanted evaporative emissions from the evaporative emissions system. Line 1322 represents a threshold pressure that, if reached after the threshold vacuum is reached and the evaporative emissions system is sealed, may indicate the presence of non-significant unwanted evaporative emissions from the evaporative emissions system.

[0188] Timeline 1300 also includes a curve 1325 that indicates the pressure in the fuel system over time as monitored via a fuel tank pressure transducer (FTPT) (e.g., 291). The pressure in the evaporative emission system and the fuel system may be at atmospheric pressure (atm) or may be negative relative to atmospheric pressure. Timeline 1300 also includes a curve 1330 that indicates whether the conditions for performing a variable vacuum diagnostic are met, as described above with respect to Figure 4 As discussed above. Timeline 1300 also includes a curve 1335, which indicates whether population data has been retrieved (yes or no) by the vehicle's controller (discussed herein as the diagnosed vehicle or VD). Timeline 1300 also includes a curve 1340, which indicates the average fuel system pressure retrieved from the population over time. Prior to retrieving such pressure indications from the population, such measurements may be "not applicable" (n / a). Additionally, the fuel system pressure from the population may be at atmospheric pressure, or positive or negative relative to atmospheric pressure. Timeline 1300 also includes a curve 1345, which indicates whether the fuel system pressure from the VD correlates (yes) (e.g., within 5%) or does not correlate (no) with the population fuel system pressure (population data) over time. Timeline 1300 also includes a curve 1350, which indicates whether undesirable evaporative emissions are present (yes) or absent (no) in the VD evaporative emissions system over time. Timeline 1300 also includes a curve 1355 that indicates whether undesirable evaporative emissions are present (yes) or absent (no) in the VD fuel system over time. Timeline 1300 also includes a curve 1360 that indicates the state of the VD controller (awake or asleep) over time.

[0189] At time t0, it will be appreciated that the VD controller is in a key-off state and does not indicate that conditions are met for performing a variable vacuum-based diagnostic. In other words, it will be appreciated that conditions may be such that performing a variable vacuum diagnostic may undesirably load the fuel vapor storage canister to a point that may increase undesirable blowdown emissions. More specifically, it will be appreciated that the VD controller has consulted lookup table 600 and indicates that conditions are not met for performing a variable vacuum diagnostic. For example, the ambient temperature may be high, and the canister load state may be high.

[0190] Therefore, between time t0 and t1, it can be understood that the VD controller schedules the controller to wake up (e.g., by setting a timer) to perform population-based fuel system diagnostics after a predetermined duration. Thus, at time t1, the controller is placed in a sleep state (curve 1360) for the predetermined duration.

[0191] After the predetermined duration has elapsed, at time t2, the controller is awakened (curve 1360). Furthermore, the vacuum pump is activated (curve 1305) and the CVV is closed (curve 1310). The FTIV is maintained closed (curve 1325). Although not specifically shown, the CPV (e.g., 261) is also commanded or maintained closed. With the vacuum pump activated, a negative pressure relative to atmospheric pressure is drawn into the evaporative emissions system (curve 1320). At time t3, the pressure in the evaporative emissions system reaches the threshold vacuum (represented by line 1321). Consequently, no significant, undesirable evaporative emissions are indicated (curve 1350).

[0192] In response to the indication of the absence of severe, undesirable evaporative emissions, the vacuum pump is deactivated, thereby sealing the evaporative emissions system from the atmosphere. Therefore, between times t3 and t4, pressure loss in the evaporative emissions system is monitored. Between times t3 and t4, pressure remains below a pressure loss threshold (represented by line 1322), thereby indicating the absence of non-severe, undesirable evaporative emissions originating from the evaporative emissions system (curve 1350). In response to the indication of the absence of both severe and non-severe, undesirable evaporative emissions from the evaporative emissions system, the CVV is commanded open (curve 1310), thereby releasing pressure in the evaporative emissions system to the atmosphere between times t4 and t5.

[0193] At time t5, the pressure in the fuel system approaches atmospheric pressure. In other words, the absolute value of the pressure is no greater than one or more predetermined pressure thresholds, such as positive or negative pressure thresholds. If the positive or negative pressure thresholds are reached, this may indicate the absence of undesirable evaporative emissions from the fuel system. However, because the pressure approaches atmospheric pressure, it is unclear whether the pressure is approaching atmospheric pressure due to ambient conditions or due to undesirable evaporative emissions from the fuel system.

[0194] Therefore, starting from time t5, a group-based fuel system diagnosis is performed. Specifically, the vehicle controller can retrieve group data related to fuel system pressure from multiple vehicles within a predetermined distance of VD. Figure 7Detailed details for generating the population and for retrieving and processing data related to fuel system pressure from the population are described at . For the sake of brevity, these details are not repeated here. Between times t5 and t6, data from the population is processed and indicates an average population fuel system pressure (curve 1340). At time t6, the VD controller indicates that the fuel system pressure data retrieved from the population does not correlate with the fuel system pressure data retrieved from the VD (e.g., differs by greater than 5%) (curve 1345). In other words, the VD's FTPT indicates a fuel system pressure close to atmospheric pressure, while the data from the population indicates a fuel system pressure that is positive relative to atmospheric pressure. Therefore, undesirable evaporative emissions are indicated for the VD fuel system (curve 1355). More specifically, if the VD's fuel system were free of undesirable evaporative emissions, it would be expected that the pressure in the fuel system would be similar in direction and magnitude to the population fuel system pressure data. The fact that the VD fuel system pressure is close to atmospheric pressure while the population indicates a positive fuel system pressure indicates that the VD fuel system has a source of undesirable evaporative emissions. However, it may not indicate whether this source of undesirable evaporative emissions includes severe or less severe emissions. Therefore, indicating undesirable evaporative emissions (without specifying severe or non-severe), a flag may be set at the controller and the MIL may be illuminated at the vehicle instrument panel to alert the vehicle driver of a request for vehicle service.

[0195] At time t7 , the controller returns to the sleep state and maintains the vehicle off between time t7 and t8 .

[0196] Now turn Figure 14, shows an exemplary timeline 1400 for performing an active variable vacuum evaporative emissions test. Timeline 1400 includes a curve 1405 that indicates whether a key-off event is indicated (yes) or not indicated (no) over time. Timeline 1400 also includes a curve 1410 that indicates whether the vehicle's engine is on or off over time. It will be understood that in this example, "on" refers to the engine burning air and fuel. Timeline 1400 also includes a curve 1415 that indicates whether conditions for performing an active variable vacuum diagnostic for the presence or absence of undesirable evaporative emissions from the fuel system are met (yes) or not met (no) over time. Timeline 1400 also includes a curve 1420 that indicates whether a vacuum pump (e.g., 289) is on or off over time. Timeline 1400 also includes: curve 1425, which indicates the CVV state over time; curve 1430, which indicates the CPV state over time; and curve 1435, which indicates the FTIV state over time. In the case of each of curves 1425, 1430, and 1435, the state can be open or closed. Timeline 1400 also includes curve 1440, which indicates the fuel vapor canister load state over time. Over time, the canister load can increase (+) or decrease (-). Timeline 1400 also includes curve 1445, which indicates the ambient temperature over time. Over time, the ambient temperature can increase (+) or decrease (-). Timeline 1400 also includes curve 1450, which indicates the fuel system pressure over time as monitored via a fuel tank pressure transducer (FTPT). The fuel system pressure can be at atmospheric pressure, or can be positive (+) or negative (-) relative to atmospheric pressure. Line 1451 represents a threshold vacuum that, if reached, may indicate the absence of non-severe, undesirable evaporative emissions. Furthermore, line 1451 may include a variable vacuum threshold based on the canister's loading status and ambient temperature. Line 1452 represents a pressure threshold that, if reached after the variable vacuum threshold is reached and further in response to the fuel system being sealed, may indicate the presence of undesirable evaporative emissions. Accordingly, curve 1455 indicates the presence (yes) or absence (no) of undesirable evaporative emissions from the fuel system over time.

[0197] At time t0, the vehicle is in operation (curve 1405), with the engine combusting air and fuel (curve 1410). Conditions for conducting an active variable vacuum evaporative emissions test have not yet been met (curve 1415). The vacuum pump (e.g., 289) is off (curve 1420), the CVV is open (curve 1425), the CPV is closed (curve 1430), and the FTIV is closed (curve 1435). The fuel vapor canister is less than half full (curve 1440), the ambient temperature is high (curve 1445), and the fuel system pressure is slightly positive relative to atmospheric pressure (curve 1450). For example, despite the high ambient temperature, there may be factors, such as wind, that can counteract the pressure buildup in the fuel system due to the high ambient temperature. Currently, no undesirable evaporative emissions are indicated in the fuel system (curve 1455).

[0198] At time t1, the engine is deactivated or shut down (plot 1410). Because no key-off event is indicated, it is understood that the vehicle is operating in a pure electric mode of operation, wherein the motor (e.g., 120) is operating to propel the vehicle. At time t2, it is indicated that the conditions for conducting an active variable vacuum evaporative emissions test are indicated. Figure 10 The conditions for performing such a test are described in detail at t2 and, therefore, will not be repeated here. In short, it will be appreciated that the vehicle is traveling on a learned route and wherein the predicted or learned stop is less than a threshold duration (e.g., less than 45 minutes) such that a quick test for undesirable evaporative emissions is desirable. In the event that the conditions for performing active variable vacuum aspiration are met at time t2, the vacuum pump is enabled or turned on (curve 1420), the CVV is commanded to close (curve 1425), and the FTIV is commanded to open (curve 1435). It will be appreciated that the conditions may be met based on the canister loading state and the ambient temperature, and it will be further appreciated that the target vacuum level may be a function of the ambient temperature (or fuel temperature in some examples) and the canister loading state. For example, in this exemplary timeline 1400, based on the ambient temperature and the canister loading state, the target vacuum may include -24 InH2O. In other words, turning to Figure 6 , ambient conditions may include 85°F, and the canister may be anywhere from 31% full to 60% full, so the target vacuum may include -24 InH2O.

[0199] Therefore, between times t2 and t3, the pressure in the fuel system and the evaporative emissions system is reduced via the vacuum pump, and the target vacuum is achieved and maintained. In other words, it can be understood that the vacuum pump can control the evacuation of the fuel system and the evaporative emissions system so that the target vacuum or threshold vacuum is maintained until the key-off event. Between times t2 and t3, as fuel vapor is drawn from the fuel tank into the fuel vapor canister, the canister load increases (plot 1440).

[0200] At time t3, a key-off event is indicated (curve 1405), and the vacuum pump is turned off, thereby isolating the fuel system and the evaporative emissions system from the atmosphere. Additionally, at time t3, the FTIV is commanded to close, isolating the fuel system from the evaporative emissions system. Between times t3 and t4, pressure loss in the fuel system is monitored, and at time t4, no undesirable evaporative emissions from the fuel system are indicated (curve 1455) because the pressure loss remains below the pressure loss threshold (line 1452). With no undesirable evaporative emissions from the fuel system indicated, at time t4, the CVV and FTIV are commanded to open (curve 1425), and the conditions for performing the active variable vacuum purge test (curve 1415) are no longer indicated. With the CVV and FTIV open, pressure in the fuel system (and the evaporative emissions system) returns to atmospheric pressure between times t4 and t5 (curve 1450). Furthermore, when the pressure is relieved, fresh air can be drawn across the fuel vapor canister due to the negative pressure in the fuel system and the evaporative emissions system, thereby desorbing at least a portion of the vapor stored in the canister to the fuel tank (plot 1440). At time t5, the FTIV is commanded to close via the controller to isolate the fuel system from the evaporative emissions system and the atmosphere. Between times t5 and t6, the vehicle is maintained in a closed state (plot 1405).

[0201] In this way, testing for the presence or absence of undesirable evaporative emissions from the vehicle's fuel system and / or evaporative emissions system may be performed such that potential false faults are reduced or eliminated.

[0202] A technical effect is the recognition that, for vehicles equipped with steel fuel tanks, the vacuum applied to the fuel system to test for the presence or absence of undesirable evaporative emissions is greater than when the fuel tank is plastic or made of some other material. By applying a variable vacuum (e.g., a larger target vacuum) to the fuel system when the fuel system includes a steel fuel tank, a greater signal-to-noise ratio can be achieved when monitoring pressure loss in the fuel system after evacuating the fuel system to a target vacuum (threshold vacuum) and sealing the fuel system (and the evaporative emissions system, in some examples). More specifically, fuel volatility can contribute to loss (loss rate or absolute loss), but this loss may not be noticeable when a larger vacuum is applied to the fuel system, such as in conditions of high ambient temperature. Another technical effect is the recognition that drawing a large vacuum on a steel fuel tank positioned in the fuel system can draw fuel vapor from the fuel tank into a fuel vapor storage canister. Particularly for hybrid applications where engine operating time is limited, it may be undesirable to load the canister with fuel vapor to a level that could result in blow-through emissions under certain conditions (e.g., high ambient temperature). Therefore, any variable vacuum applied to the fuel system of such a vehicle may be a function not only of ambient temperature, but also of the current canister filling state, conditioned upon utilizing a vacuum pump (e.g., 289) to evacuate the fuel system (and evaporative emissions system). By factoring the canister filling state into the variable vacuum determination, a balance may be achieved between the desired signal-to-noise ratio for testing for undesirable evaporative emissions and the desired canister filling state as ambient conditions change. In this way, undesirable evaporative emissions may be reduced or eliminated, and the completion rate of testing for the presence or absence of undesirable evaporative emissions may be increased.

[0203] Yet another technical effect is the recognition that, in situations where utilizing a variable vacuum target may undesirably load the canister, population-based diagnostics can be utilized to infer whether the fuel system of a diagnosed vehicle has a source of undesirable evaporative emissions. For example, one technical effect is the recognition that fuel system pressure data from a population of vehicles within a predetermined distance of the diagnosed vehicle can be compared to the fuel system pressure from the diagnosed vehicle, which can enable a determination of whether the fuel system of the diagnosed vehicle has a source of undesirable evaporative emissions originating from the fuel system.

[0204] Yet another technical effect is the recognition that there may be situations where a vehicle may be stopped for a period not sufficient to carry out Figure 5 The variable vacuum based test discussed (the test is started a predetermined duration (which may include several hours) after key off), Figure 7The duration of the population-based diagnostic, or EONV test, discussed herein. In such an example, an active variable vacuum purge test may be performed such that the test can be expected to be completed within a certain duration. The duration may include a learned duration of a particular stop that may be learned via the route learning method discussed above. By varying the target vacuum for such an active variable vacuum test based on ambient temperature and canister loading status, the test results may be robust without undesirably loading the fuel vapor canister, as discussed. In such an example, V2X communication between vehicles may be utilized to obtain data related to recent similar diagnostics performed on other similarly located vehicles (e.g., vehicles of the same make / model, vehicles within a predetermined threshold distance of the vehicle, etc.), wherein the active variable vacuum test is performed in response to an indication that a particular vacuum level is desirable to obtain robust results from the test diagnostic.

[0205] In this article and reference Figures 1 to 3 The system described herein and with reference to Figures 4 and 5 and Figures 7 to 10The described method can implement one or more systems and one or more methods. In one example, a method includes testing for undesirable evaporative emissions originating from a fuel system by: purging a vehicle's fuel system to a variable vacuum level through an entire fuel vapor canister configured to capture and store fuel vapor in a first operating mode; and purging the fuel system to the variable vacuum level through a portion of the fuel vapor canister in a second operating mode. In the first example of the method, the method further includes learning a common route traveled by the vehicle, wherein the learned route includes one or more learned key-off events and also includes expected durations of the one or more learned key-off events; and wherein purging the fuel system in both the first operating mode and the second operating mode is responsive to the learned key-off event duration being less than a threshold key-off duration. A second example of the method optionally includes the first example and further includes purging the fuel system in both the first operating mode and the second operating mode includes purging the fuel system before the key-off event, then sealing the fuel system, and monitoring a pressure loss and / or a rate of pressure loss in the fuel system to indicate whether undesirable evaporative emissions originate from the fuel system. A third example of the method optionally includes any one or more or each of the first to second examples, and further includes, wherein purging the fuel system to the variable vacuum level in both the first and second operating modes is based at least in part on vehicle-to-vehicle communication indicating that the variable vacuum level is desirable for robustness of the test. A fourth example of the method optionally includes any one or more or each of the first to third examples, and further includes, wherein the variable vacuum level in the first operating mode is a function of the state of charge of the fuel vapor canister and fuel volatility; and wherein the variable vacuum level in the second operating mode is a function of fuel volatility but is independent of the state of charge of the fuel vapor canister. A fifth example of the method optionally includes any one or more or each of the first to fourth examples, and further includes, wherein purging the fuel system in the first operating mode is performed via a vacuum pump positioned between the fuel vapor canister and atmosphere; and wherein purging the fuel system in the second operating mode is performed via the engine.A sixth example of the method optionally includes any one or more or each of the first to fifth examples, and further includes, wherein the vacuum pump is positioned in a vacuum pump conduit, the vacuum pump being connected in parallel with a canister vent valve positioned in a vent line between the fuel vapor canister and atmosphere; and wherein the canister vent valve is commanded to close immediately prior to purging the fuel system in the first operating mode. A seventh example of the method optionally includes any one or more or each of the first to sixth examples, and further includes, when the vehicle is operating in an electric-only operating mode, activating the engine to combust air and fuel to purge the fuel system in the second operating mode.

[0206] Another example of a method includes: operating a vehicle in a first mode to purge a fuel system of the vehicle to a first variable vacuum level for testing for undesirable evaporative emissions from the fuel system during a first operating condition, wherein purging the fuel system in the first mode further charges a fuel vapor storage canister with fuel vapor from the fuel system; and operating the vehicle in a second mode to purge the fuel system of the vehicle to a second variable vacuum level for testing for undesirable evaporative emissions during a second operating condition, wherein purging the fuel system in the second mode avoids further charging the fuel vapor storage canister with fuel vapor from the fuel system. In the first example of the method, the method includes wherein the first variable vacuum level is a function of a state of charge of the fuel vapor storage canister and fuel volatility; and wherein the second variable vacuum level is a function of the fuel volatility but is independent of the state of charge of the fuel vapor storage canister. A second example of the method optionally includes the first example, and further includes, wherein the first operating condition includes the state of charge of the fuel vapor storage canister combined with fuel volatility being less than a combined threshold; and wherein the second operating condition includes the state of charge of the fuel vapor storage canister combined with fuel volatility being greater than the combined threshold. A third example of the method optionally includes any one or more or each of the first to second examples, and further includes, purging the fuel system in both the first mode and the second mode in response to a request to perform the test, and further in response to an indication that a learned key-off event has a duration less than a threshold key-off duration. A fourth example of the method optionally includes any one or more or each of the first to third examples, and further includes, wherein purging the fuel system in both the first and second operating conditions includes: purging the fuel system to the first variable vacuum level or the second variable vacuum level, respectively, immediately prior to the learned key-off event; and, in response to the key-off event, sealing the fuel system and indicating the presence or absence of undesirable evaporative emissions based on a pressure loss or a rate of pressure loss in the fuel system. A fifth example of the method optionally includes any one or more or each of the first to fourth examples, and further includes, wherein purging the fuel system under the first operating condition is performed via a vacuum pump positioned between the fuel vapor canister and atmosphere; and wherein purging the fuel system under the second operating condition is performed via the engine. A sixth example of the method optionally includes any one or more or each of the first to fifth examples, and further includes, wherein the engine is one of burning air and fuel or rotating without fuel via an electric motor.A seventh example of the method optionally includes any one or more or each of the first through sixth examples, and further includes wherein the vacuum pump is positioned in a vacuum pump conduit, the vacuum pump being connected in parallel with a canister vent valve positioned in a vent line between the fuel vapor canister and atmosphere; and wherein the canister vent valve is commanded closed immediately prior to purging the fuel system in the first mode. An eighth example of the method optionally includes any one or more or each of the first through seventh examples, and further includes wherein purging the fuel system to the second variable vacuum further includes an indication that a temperature of an exhaust catalyst is greater than a threshold temperature. A ninth example of the method optionally includes any one or more or each of the first through eighth examples, and further includes, if the temperature of the exhaust catalyst is below the threshold temperature, activating a heating element of the exhaust catalyst to raise the temperature of the exhaust catalyst to greater than the threshold temperature.

[0207] A system for a hybrid electric vehicle comprises: a fuel system including a fuel tank for storing fuel; an evaporative emission system including a fuel vapor canister, the evaporative emission system being selectively fluidically coupled to the fuel system via a fuel tank isolation valve; a vent line originating from the fuel vapor canister, the vent line including a canister vent valve configured to selectively fluidly couple the fuel vapor canister to atmosphere; an engine, an air intake of the engine being selectively fluidically coupled to the evaporative emission system via a canister purge valve; a fuel tank pressure transducer positioned in the fuel system; and a vacuum pump positioned in the and a control unit configured to control the flow of fuel from the fuel system to a desired flow rate. The control unit comprises a first control unit configured to control the flow of fuel from the fuel system to a desired flow rate. The control unit comprises a first control unit configured to control the flow of fuel from the fuel system to a desired flow rate. The control unit comprises a first control unit configured to control the flow of fuel from the fuel system to a desired flow rate. The control unit comprises a second control unit configured to control the flow of fuel from the fuel system to a desired flow rate. and evacuating the fuel system through the entire fuel vapor canister in a first mode under conditions where the fuel vapor canister is loaded with fuel vapor, and evacuating the fuel system through a portion of the fuel vapor canister in a second mode under a second operating condition to avoid undesirably loading the fuel vapor canister with fuel vapor; wherein evacuating the fuel system in the first mode includes evacuating the fuel system to a first variable vacuum target by commanding the canister vent valve to close, commanding the fuel tank isolation valve to open, commanding the canister purge valve to close, and actuating the vacuum pump to evacuate the fuel system to a negative pressure relative to atmospheric pressure, wherein the variable The vacuum target is a function of fuel volatility and a state of charge of the fuel vapor canister, and wherein the first check valve and the second check valve open in response to actuating the vacuum pump and close in response to actuating the vacuum pump off; and wherein purging the fuel system in the second mode includes purging the fuel system to a second variable vacuum target via commanding the canister purge valve to open, commanding the canister vent valve to close, commanding the fuel tank isolation valve to open, and purging the fuel system via vacuum derived from operation of the engine, wherein the second variable vacuum target is a function of fuel volatility but is independent of the state of charge of the fuel vapor canister.In a first example of the system, the system further includes wherein the controller stores further instructions for evacuating the fuel system to the first variable vacuum level or the second variable vacuum level in both the first mode and the second mode, respectively, just prior to a learned key-off event, wherein a learned duration of the learned key-off event is less than a threshold key-off duration; and wherein in response to the learned key-off event in both the first mode and the second mode, the fuel system is sealed and the presence or absence of undesirable evaporative emissions is indicated based on a pressure loss or a rate of pressure loss in the fuel system.

[0208] In another representation, a method includes evacuating the fuel system to a first variable vacuum level (optionally a function of ambient temperature and / or other parameters) in a first, more filled state of the canister (a first operating condition), and evacuating the fuel system to a second variable vacuum level (which may be a function of ambient temperature and the state of filling of the canister) in a second, less filled state of the canister (a second operating condition).

[0209] In a first example of the above method, the method further includes: in response to reaching or exceeding the first variable vacuum level or reaching or exceeding the second variable vacuum level, indicating the absence of significant undesirable evaporative emissions from the fuel system during both the first operating condition and the second operating condition. A second example of the method optionally includes the first example and further includes, wherein in response to reaching or exceeding the first variable vacuum level or reaching or exceeding the second variable vacuum level during both the first operating condition and the second operating condition, maintaining the first variable vacuum level or the second variable vacuum level until a key-off event is indicated, then sealing the fuel system, and indicating the presence or absence of non-severe undesirable evaporative emissions from the fuel system based on a pressure loss or a rate of pressure loss in the fuel system. A third example of the method optionally includes any one or more or each of the first and second examples and further includes, wherein the first operating condition includes purging the fuel system via engine intake manifold vacuum, and wherein the second operating condition includes purging the fuel system via a vacuum pump positioned in a vent line between the fuel vapor canister and atmosphere in the evaporative emissions system. A fourth example of the method optionally includes any one or more or each of the first through third examples, and further includes learning or predicting a route that the vehicle typically travels, and wherein the first operating condition and / or the second operating condition includes an indication that a learned key-off duration along the learned route that the vehicle is currently traveling is less than a threshold duration. A fifth example of the method optionally includes any one or more or each of the first through fourth examples, and further includes wherein operating the vehicle in the first operating condition draws fuel vapor from the fuel tank through a portion of the fuel vapor canister, and wherein operating the vehicle in the second operating condition draws fuel vapor from the fuel tank through the entire fuel vapor canister. A sixth example of the method optionally includes any one or more or each of the first through fifth examples, and further includes wherein the first operating condition being above the threshold includes a condition where purging the fuel system through the entire fuel vapor canister fills the canister to an undesirable level.

[0210] In yet another embodiment, a method includes: indicating a charge state of a fuel vapor canister positioned in an evaporative emission system of a vehicle and indicating an ambient temperature in response to a key-off event; and operating the vehicle in a first mode to perform a population-based diagnostic test for the presence or absence of undesirable evaporative emissions in the vehicle's fuel system under a first operating condition including an indication that a combination of the charge state of the fuel vapor canister and the ambient temperature is above a combined threshold, and operating the vehicle in a second mode to perform a population-based diagnostic test for the presence or absence of undesirable evaporative emissions in the fuel system by evacuating the fuel system to a variable vacuum level via a vacuum pump positioned in a vent line in the evaporative emission system between the fuel vapor canister and atmosphere under a second operating condition including an indication that the combination of the charge state of the fuel vapor canister and the ambient temperature is below the threshold. In the first example of the method, the method further includes: wherein operating the vehicle in the first mode to perform the population-based diagnostic test does not result in further charging of the fuel vapor canister, and wherein operating the vehicle in the second mode to perform the diagnostic test further charges the fuel vapor canister. A second example of the method optionally includes the first example and further includes, wherein operating the vehicle in the second mode further includes: fluidly coupling the fuel system to the evaporative emissions system to evacuate the fuel system to the variable vacuum level, and wherein in response to reaching or exceeding the variable vacuum level, the fuel system is sealed from the evaporative emissions system, and the presence or absence of undesirable evaporative emissions from the fuel system is indicated based on a loss of pressure in the fuel system for a predetermined duration. A third example of the method optionally includes any one or more or each of the first and second examples and further includes, wherein operating the vehicle in the first mode includes: a controller of the vehicle sending a wireless request for one or more data sets related to fuel system pressure from a plurality of vehicles within a threshold distance of the vehicle; receiving the one or more data sets; and indicating the presence of undesirable evaporative emissions from the fuel system of the vehicle in response to the one or more data sets related to fuel system pressure not being correlated with fuel system pressure in the vehicle for a predetermined duration. A fourth example of the method optionally includes any one or more or each of the first to third examples, and further includes an indication that operating the vehicle in the first mode includes an absolute value of the pressure in the fuel system of the vehicle being no greater than a positive pressure threshold or a negative pressure threshold immediately prior to performing the population-based test diagnostic.A fifth example of the method optionally includes any one or more or each of the first to fourth examples, and further includes, wherein operating the vehicle in the first mode or the second mode includes: waking the controller after a predetermined sleep duration. A sixth example of the method optionally includes any one or more or each of the first to fifth examples, and further includes, wherein operating the vehicle in the first mode or the second mode also includes an indication of an absence of severe and / or non-severe undesirable evaporative emissions from the evaporative emissions system of the vehicle.

[0211] In yet another embodiment, a method includes testing a fuel system of a vehicle for the presence or absence of undesirable evaporative emissions by purging the fuel system of the vehicle to a variable vacuum level during a condition in which the engine of the vehicle is not operating, the variable vacuum level being a function of ambient temperature and a charge state of a fuel vapor canister located in the evaporative emissions system of the vehicle. In a first example of the method, the method further includes wherein purging the fuel system to the variable vacuum level comprises an indication that the evaporative emissions system is free of undesirable evaporative emissions. A second example of the method optionally includes the first example and further includes wherein, under a first operating condition including a condition in which the engine is not operating but in which the vehicle is electrically propelled, the vehicle is operated in a first mode to purge the fuel system to the variable vacuum level just prior to a predicted or learned key-off event, and under a second operating condition including a key-off condition, the vehicle is operated in a second mode to purge the fuel system to the variable vacuum level after a controller of the vehicle awakens from a sleep mode after a predetermined sleep duration. A third example of the method optionally includes any one or more or each of the first to second examples, and further includes wherein the predicted or learned key-off event is predicted to have a duration less than a predetermined duration. A fourth example of the method optionally includes any one or more or each of the first to third examples, and further includes wherein operating the vehicle in both the first mode and the second mode includes actuating open a vacuum pump located in a vent line of the evaporative emissions system between the fuel vapor canister and atmosphere, and further includes fluidly coupling the fuel system to the evaporative emissions system. A fifth example of the method optionally includes any one or more or each of the first to fourth examples, and further includes wherein operating the vehicle in both the first mode and the second mode includes sealing the fuel system from the evaporative emissions system after reaching the variable vacuum level, and indicating the presence or absence of undesirable evaporative emissions based on a loss of pressure in the fuel system for a predetermined duration. A sixth example of the method optionally includes any one or more or each of the first through fifth examples and further includes wherein the variable vacuum level increases with increasing ambient temperature and increases with decreasing state of charge of the fuel vapor canister.

[0212] In yet another representation, a method includes testing for the presence or absence of undesirable evaporative emissions from a fuel system of a vehicle based on a load state of a fuel vapor canister positioned in the evaporative emissions system of the vehicle and an ambient temperature. In a first example of the method, the method further includes performing the test in response to an indication that the evaporative emissions system of the vehicle is free of undesirable evaporative emissions. A second example of the method optionally includes the first example and further includes wherein performing the test includes the condition that a pressure in the fuel system is no greater than a positive pressure threshold or a negative pressure threshold in a condition in which the fuel system is sealed from the evaporative emissions system of the vehicle and the vehicle is in a key-off state. A third example of the method optionally includes any one or more or each of the first and second examples and further includes wherein performing the test includes purging the fuel system via a vacuum pump positioned in a vent line in the evaporative emissions system between the fuel vapor canister and atmosphere, and wherein purging the fuel system includes fluidly coupling the fuel system to the evaporative emissions system. A fourth example of the method optionally includes any one or more or each of the first through third examples, and further includes not performing the test in response to a combination of ambient temperature and the state of charge of the fuel vapor canister being above a threshold. A fifth example of the method optionally includes any one or more or each of the first through fourth examples, and further includes evacuating the fuel system to a variable vacuum level via the vacuum pump, the variable vacuum level being a function of the state of charge of the fuel vapor canister and ambient temperature. A sixth example of the method optionally includes any one or more or each of the first through fifth examples, and further includes wherein performing the test includes: isolating the fuel system from the evaporative emissions system in response to reaching the variable vacuum level, and indicating the presence or absence of undesirable evaporative emissions from the fuel system based on a loss of pressure in the fuel system for a predetermined duration. A seventh example of the method optionally includes any one or more or each of the first to sixth examples, and further includes wherein performing the test comprises: evacuating the fuel system to the variable vacuum level just prior to a key-off event, wherein the key-off event comprises a predicted or learned key-off event having a duration less than a threshold duration, and wherein the fuel system is sealed in response to an indication of the key-off event to monitor a pressure loss in the fuel system for an indication of the presence or absence of undesirable evaporative emissions.

[0213] In yet another embodiment, a method includes performing a variable vacuum diagnostic for the presence or absence of undesirable evaporative emissions from a fuel system of a vehicle during an engine-off state, the variable vacuum diagnostic comprising purging the fuel system to a variable vacuum level that is a function of ambient temperature and a load state of a fuel vapor canister located in the evaporative emission system of the vehicle; and adjusting a purge schedule of the fuel vapor canister based on reaching the variable vacuum level during the purge. In a first example of the method, the method further includes scheduling a purge event to occur more quickly after completing the variable vacuum diagnostic in response to purging the fuel system to a greater variable vacuum level than in a case where the fuel system is purged to a lesser variable vacuum level. A second example of the method optionally includes the first example and further includes purging the fuel system comprising fluidly coupling the fuel system to the evaporative emission system, and purging the fuel system further charges the canister with fuel vapor. A third example of the method optionally includes any one or more or each of the first and second examples, and further includes, wherein purging the fuel system to the variable vacuum level is performed via a vacuum pump positioned in a vent line in the evaporative emissions system, the vent line being positioned between the fuel vapor canister and the atmosphere. A fourth example of the method optionally includes any one or more or each of the first to third examples, and further includes, wherein the engine-off state includes a key-off state, or a state in which the vehicle is electrically propelled. A fifth example of the method optionally includes any one or more or each of the first to fourth examples, and further includes, wherein in response to reaching the variable vacuum level while the vehicle is electrically propelled, maintaining the variable vacuum level until a key-off event is indicated, then stopping the purging, isolating the fuel system from the evaporative emissions system, and indicating the presence or absence of undesirable evaporative emissions based on a loss of pressure in the fuel system for a predetermined duration. A sixth example of the method optionally includes any one or more or each of the first to fifth examples, and further includes wherein performing the variable vacuum diagnostic during the key-off state includes: waking a controller of the vehicle a determined duration after the key-off state, evacuating the fuel system to the variable vacuum level, and then sealing the fuel system to indicate the presence or absence of undesirable evaporative emissions based on a loss of pressure in the fuel system for the predetermined duration.

[0214] It should be noted that the exemplary control and estimation routines included herein can be used with various engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in a non-transitory memory and can be implemented by a control system including a controller in conjunction with various sensors, actuators, and other engine hardware. The specific routines described herein may represent one or more of any number of regulation strategies (such as event-driven, intermittently driven, multi-tasking, multi-threading, etc.). Thus, the various actions, operations, and / or functions shown may be performed in the order shown, in parallel, or in some cases, omitted. Similarly, the regulation order is not necessarily required to achieve the features and advantages of the exemplary embodiments described herein, but is provided for ease of illustration and description. One or more of the actions, operations, and / or functions shown may be repeatedly performed depending on the specific strategy used. In addition, the described actions, operations, and / or functions may graphically represent code to be programmed into the non-transitory memory of a computer-readable storage medium in the engine control system, wherein the described actions are implemented by executing the instructions in conjunction with an electronic controller in a system including various engine hardware components.

[0215] It should be understood that the configurations and routines disclosed herein are exemplary in nature, and these specific embodiments should not be considered limiting, as many variations are possible. For example, the above technology can be applied to V-6, inline-4, inline-6, V-12, opposed-4, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or properties disclosed herein.

[0216] The following claims particularly point out certain combinations and subcombinations believed to be novel and non-obvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amendment of the present claims or by presentation of new claims in this or a related application. Such claims, whether broader, narrower, the same, or different in scope than the original claims, are also deemed to be included within the subject matter of the present disclosure.

[0217] According to the present invention, a method includes testing for undesirable evaporative emissions from a fuel system by purging a vehicle's fuel system to a variable vacuum level through an entire fuel vapor canister configured to capture and store fuel vapor in a first operating mode, and purging the fuel system to the variable vacuum level through a portion of the fuel vapor canister in a second operating mode.

[0218] According to one embodiment, the above invention is further characterized by learning a common route along which the vehicle is traveled, wherein the learned route includes one or more learned key-off events and also includes expected durations of the one or more learned key-off events, and wherein purging the fuel system in both the first operating mode and the second operating mode is responsive to the learned key-off event duration being below a threshold key-off duration.

[0219] According to one embodiment, purging the fuel system in both the first and second operating modes includes purging the fuel system prior to the key-off event, then sealing the fuel system, and monitoring a pressure loss and / or a rate of pressure loss in the fuel system to indicate whether undesirable evaporative emissions are originating from the fuel system.

[0220] According to one embodiment, evacuating the fuel system to the variable vacuum level in both the first and second operating modes is based at least in part on vehicle-to-vehicle communications indicating that the variable vacuum level is desirable for robustness of the test.

[0221] According to one embodiment, the variable vacuum level in the first operating mode is a function of the state of charge of the fuel vapor canister and fuel volatility; and wherein the variable vacuum level in the second operating mode is a function of fuel volatility but is independent of the state of charge of the fuel vapor canister.

[0222] According to one embodiment, purging the fuel system in the first operating mode is performed via a vacuum pump positioned between the fuel vapor canister and atmosphere; and wherein purging the fuel system in the second operating mode is performed via the engine.

[0223] According to one embodiment, the vacuum pump is positioned in a vacuum pump conduit, the vacuum pump being connected in parallel with a canister vent valve positioned in a vent line between the fuel vapor canister and atmosphere; and wherein the canister vent valve is commanded to close just prior to purging the fuel system in the first operating mode.

[0224] According to one embodiment, the above invention is further characterized by enabling the engine to combust air and fuel in a case where the vehicle is operated in a purely electric operating mode so as to purge the fuel system in the second operating mode.

[0225] According to the present invention, a method includes: operating a vehicle in a first mode under a first operating condition to evacuate a fuel system of the vehicle to a first variable vacuum level for testing for undesirable evaporative emissions originating from the fuel system, wherein evacuating the fuel system in the first mode further charges a fuel vapor storage canister with fuel vapor from the fuel system; and operating the vehicle in a second mode under a second operating condition to evacuate the fuel system of the vehicle to a second variable vacuum level for performing the test for undesirable evaporative emissions, wherein evacuating the fuel system in the second mode avoids further charging the fuel vapor storage canister with fuel vapor from the fuel system.

[0226] According to one embodiment, the first variable vacuum level is a function of the state of charge of the fuel vapor storage canister and fuel volatility; and wherein the second variable vacuum level is a function of the fuel volatility but is independent of the state of charge of the fuel vapor storage canister.

[0227] According to one embodiment, the first operating condition comprises the state of charge of the fuel vapor storage canister in combination with fuel volatility being below a combined threshold; and wherein the second operating condition comprises the state of charge of the fuel vapor storage canister in combination with fuel volatility being greater than the combined threshold.

[0228] According to one embodiment, purging the fuel system in both the first mode and the second mode is responsive to a request to perform the test and further responsive to an indication that a learned key-off event has a duration less than a threshold key-off duration.

[0229] According to one embodiment, purging the fuel system under both the first and second operating conditions includes purging the fuel system to the first variable vacuum level or the second variable vacuum level, respectively, just prior to a learned key-off event; and sealing the fuel system in response to the key-off event, and indicating the presence or absence of undesirable evaporative emissions based on a pressure loss or a rate of pressure loss in the fuel system.

[0230] According to one embodiment, purging the fuel system during the first operating condition is performed via a vacuum pump positioned between the fuel vapor canister and atmosphere; and wherein purging the fuel system during the second operating condition is performed via the engine.

[0231] According to one embodiment, the engine is one of burning air and fuel or spinning without fuel via an electric motor.

[0232] According to one embodiment, the vacuum pump is positioned in a vacuum pump conduit, the vacuum pump being connected in parallel with a canister vent valve positioned in a vent line between the fuel vapor canister and atmosphere; and wherein the canister vent valve is commanded closed just prior to purging the fuel system in the first mode.

[0233] According to one embodiment, venting the fuel system to the second variable vacuum further includes an indication that a temperature of an exhaust catalyst is greater than a threshold temperature.

[0234] According to one embodiment, the above invention is further characterized in that when the temperature of the exhaust catalyst is lower than the threshold temperature, the heating element of the exhaust catalyst is activated to increase the temperature of the exhaust catalyst to be higher than the threshold temperature.

[0235] According to the present invention, a system for a hybrid electric vehicle is provided, comprising: a fuel system including a fuel tank for storing fuel; an evaporative emission system including a fuel vapor canister, the evaporative emission system being selectively fluidically coupled to the fuel system via a fuel tank isolation valve; a vent line originating from the fuel vapor canister, the vent line including a canister vent valve configured to selectively fluidically couple the fuel vapor canister to the atmosphere; an engine, an air intake of the engine being selectively fluidically coupled to the evaporative emission system via a canister purge valve; a fuel tank pressure transducer positioned in the fuel system; and a vacuum pump. and a control unit configured to control the flow of fuel from the fuel system to a desired flow rate. The control unit comprises a first control unit configured to control the flow of fuel from the fuel system to a desired flow rate. The control unit comprises a first control unit configured to control the flow of fuel from the fuel system to a desired flow rate. The control unit comprises a first control unit configured to control the flow of fuel from the fuel system to a desired flow rate. The control unit comprises a second control unit configured to control the flow of fuel from the fuel system to a desired flow rate. and evacuating the fuel system in a first mode through the entire fuel vapor canister when the fuel vapor canister is loaded with fuel vapor, and evacuating the fuel system in a second mode through a portion of the fuel vapor canister when the fuel vapor canister is loaded with fuel vapor to avoid undesirable charging of the fuel vapor canister with fuel vapor; wherein evacuating the fuel system in the first mode includes evacuating the fuel system to a first variable vacuum target by commanding the canister vent valve to close, commanding the fuel tank isolation valve to open, commanding the canister purge valve to close, and actuating the vacuum pump to evacuate the fuel system to a negative pressure relative to atmospheric pressure, wherein the a variable vacuum target that is a function of fuel volatility and a state of charge of the fuel vapor canister, and wherein the first and second check valves open in response to actuating the vacuum pump and close in response to actuating the vacuum pump off; and wherein purging the fuel system in the second mode comprises purging the fuel system to a second variable vacuum target via commanding the canister purge valve to open, commanding the canister vent valve to close, commanding the fuel tank isolation valve to open, and purging the fuel system via vacuum derived from operation of the engine, wherein the second variable vacuum target is a function of fuel volatility but is independent of the state of charge of the fuel vapor canister.

[0236] According to one embodiment, the controller stores further instructions for evacuating the fuel system to the first variable vacuum level or the second variable vacuum level, respectively, in both the first mode and the second mode just prior to a learned key-off event, wherein a learned duration of the learned key-off event is less than a threshold key-off duration; and wherein in response to the learned key-off event in both the first mode and the second mode, the fuel system is sealed and the presence or absence of undesirable evaporative emissions is indicated based on a pressure loss or a rate of pressure loss in the fuel system.

Claims

1. A method for diagnosing evaporative emissions from a fuel system of a vehicle, comprising: testing for undesirable evaporative emissions from the fuel system by: evacuating the fuel system to a variable vacuum level across a fuel vapor canister configured to capture and store fuel vapors in a first operating mode; as well as in a second operating mode, evacuating the fuel system to the variable vacuum level through a portion of the fuel vapor canister; wherein the variable vacuum level in the first operating mode is a function of the state of charge of the fuel vapor canister and fuel volatility, and the variable vacuum level in the second operating mode is a function of fuel volatility but is independent of the state of charge of the fuel vapor canister; and In the first operating mode, purging the fuel system is performed via a vacuum pump positioned between the fuel vapor canister and the atmosphere, and in the second operating mode, purging the fuel system is performed via the engine.

2. The method of claim 1, further comprising: A common route along which the vehicle travels is learned, wherein the learned route includes one or more learned key-off events and further includes expected durations of the one or more learned key-off events. 3 . The method of claim 2 , wherein purging the fuel system in both the first operating mode and the second operating mode is responsive to a learned key-off event duration being below a threshold key-off duration.

4. The method of claim 2, wherein purging the fuel system in both the first operating mode and the second operating mode comprises: The fuel system is purged prior to the one or more learned key-off events, the fuel system is then sealed, and a pressure loss and / or a rate of pressure loss in the fuel system is monitored to indicate whether undesirable evaporative emissions are originating from the fuel system.

5. The method of claim 1 , wherein evacuating the fuel system to the variable vacuum level in both the first operating mode and the second operating mode is based at least in part on vehicle-to-vehicle communications indicating that the variable vacuum level is desirable for robustness of the test. 6 . The method of claim 1 , wherein the vacuum pump is positioned in a vacuum pump conduit, the vacuum pump being connected in parallel with a canister vent valve positioned in a vent line between the fuel vapor canister and atmosphere. 7 . The method of claim 6 , wherein the canister vent valve is commanded closed just prior to purging the fuel system in the first operating mode.

8. The method of claim 1 , further comprising: In a case where the vehicle is operating in an electric-only operating mode, the engine is enabled to combust air and fuel to purge the fuel system in the second operating mode.

9. The method of claim 1 , wherein purging the fuel system in the second operating mode further comprises an indication that a temperature of an exhaust catalyst is greater than a threshold temperature; and In a case where the temperature of the exhaust catalyst is lower than the threshold temperature, a heating element of the exhaust catalyst is activated to increase the temperature of the exhaust catalyst to above the threshold temperature.

10. A system for a hybrid electric vehicle, comprising: a fuel system comprising a fuel tank for storing fuel; an evaporative emissions system including a fuel vapor canister, the evaporative emissions system selectively fluidly coupled to the fuel system via a fuel tank isolation valve; a vent line from the fuel vapor canister, the vent line including a canister vent valve configured to selectively fluidly couple the fuel vapor canister to atmosphere; an engine having an air intake selectively fluidly coupled to the evaporative emissions system via a canister purge valve; a fuel tank pressure transducer positioned in the fuel system; a vacuum pump positioned in a vacuum pump conduit connected in parallel with the ventilation line; a first check valve positioned in the vacuum pump conduit between the vacuum pump and the vent line downstream of the canister vent valve; a second check valve positioned in the vacuum pump conduit between the vacuum pump and the vent line upstream of the canister vent valve; as well as a controller storing instructions in a non-transitory memory that, when executed, cause the controller to: testing for undesirable evaporative emissions from the fuel system in an environmentally friendly manner by purging the fuel system in a first pattern through the entire fuel vapor canister under a first operating condition where purging the fuel system would not undesirably charge the fuel vapor canister with fuel vapor, and purging the fuel system in a second pattern through a portion of the fuel vapor canister under a second operating condition to avoid undesirably charging the fuel vapor canister with fuel vapor; wherein evacuating the fuel system in the first mode includes evacuating the fuel system to a first variable vacuum level by commanding the canister vent valve to close, commanding the fuel tank isolation valve to open, commanding the canister purge valve to close, and actuating the vacuum pump to evacuate a negative pressure relative to atmospheric pressure into the fuel system, wherein the first variable vacuum level is a function of fuel volatility and a state of charge of the fuel vapor canister, and wherein the first check valve and the second check valve open in response to actuating the vacuum pump and close in response to actuating the vacuum pump to close; wherein purging the fuel system in the second mode includes purging the fuel system to a second variable vacuum level by commanding the canister purge valve to open, commanding the canister vent valve to close, commanding the fuel tank isolation valve to open, and purging the fuel system via vacuum derived from operation of the engine, wherein the second variable vacuum level is a function of fuel volatility but is independent of the state of charge of the fuel vapor canister.

11. The system of claim 10, wherein the controller stores further instructions for venting the fuel system to the first variable vacuum level or the second variable vacuum level in both the first mode and the second mode, respectively, immediately prior to a learned key-off event, wherein the learned duration of the learned key-off event is less than a threshold key-off duration; and The fuel system is sealed in response to the learned key-off events in both the first mode and the second mode, and the presence or absence of undesirable evaporative emissions is indicated based on a pressure loss or a rate of pressure loss in the fuel system.

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