System and method for air intake system hydrocarbon trap diagnostics

Abstract

The present disclosure provides a system and method for diagnosing an air intake system hydrocarbon (AIS) trap during vehicle shutdown conditions. Methods and systems are provided for diagnosing an air intake system hydrocarbon (AIS HC) trap during vehicle shutdown conditions. In one example, a method may include generating fuel vapor in a fuel tank, directing the generated vapor to the AIS HC trap, and then actively purging the AIS HC trap. Degradation of the AIS HC trap may be indicated based on the exhaust gas air-fuel ratio during the active purging of the AIS HC trap.

Description

Technical Field

[0001] The present description generally relates to methods and systems for performing diagnostics on a hydrocarbon trap coupled to an engine intake system. Background Art

[0002] In internal combustion engines, the fuel vapor canister primarily adsorbs refueling vapors, as refueling vapors and daytime vapors are sealed within the fuel tank by the fuel tank isolation valve. An air intake system hydrocarbon (AIS HC) trap can capture hydrocarbons injected by leaky injectors and / or from fuel that may be stirred in the engine's air intake. An AIS HC trap can also capture unburned fuel trapped within the engine cylinders themselves. An AIS HC trap is required for a vehicle to be classified as a practical zero-emission vehicle (PZEV).

[0003] The contents of the AIS HC trap can be flushed into the engine intake during engine operation by opening the intake throttle plate, thereby directing fresh air through the trap and desorbing bound hydrocarbons for combustion. However, hybrid vehicles can operate for extended periods without burning fuel, thus limiting the opportunity to flush the fuel vapor canister and AIS HC trap to allow for combustion. Extended periods without AIS HC trap flushing can lead to AIS HC trap degradation. Furthermore, liquid ingestion can damage the adsorbent material present in the HC trap.

[0004] Dudar discloses an exemplary method for periodically or opportunistically flushing an AIS HC trap in U.S. Patent Application No. 20170234246. During engine non-combustion conditions, the AIS HC trap is flushed into the fuel vapor canister by reverse-rotating the engine via an electric motor. The reverse engine rotation causes atmospheric air to enter the engine intake via the engine's exhaust, thereby desorbing hydrocarbons bound to the intake system's HC trap.

[0005] However, the inventors herein have recognized potential issues with such systems. As an example, when flushing an AIS HC trap, HC trap degradation is not diagnosed. Operating an engine with a degraded HC trap and flushing the degraded HC trap may result in increased effluent emissions. Summary of the Invention

[0006] In one example, the aforementioned problem can be addressed by an engine method comprising: testing for adsorbent material degradation during an unfueled engine cranking operation by directing fuel vapor to an adsorbent material located in an air intake of the engine with a throttle valve coupled to the engine air intake in a closed position, and indicating the presence or absence of adsorbent material degradation based on air-fuel ratio conditions in an exhaust system of the engine when the throttle valve is opened. In this manner, degradation of the AIS HC trap can be detected by saturating the AIS HC trap with fuel vapor during a vehicle key-off condition and then monitoring the exhaust air-fuel ratio while the AIS HC trap is being flushed.

[0007] In one example, a diagnostic routine for the AIS HC trap can be opportunistically performed during a vehicle key-off condition when the engine is not operating. The engine can be reversed to remove any remaining fuel vapor from the engine intake manifold to the atmosphere via the exhaust passage. Once the exhaust air-fuel ratio estimated by a heated exhaust gas oxygen (HEGO) sensor becomes lean of stoichiometry, indicating an absence of fuel vapor in the exhaust passage, the fuel system can be isolated and fuel vapor can be generated in the fuel tank by operating the fuel pump. In response to the fuel pressure reaching a threshold pressure, the fuel vapor from the fuel system can be directed to the AIS HC trap via a fuel vapor canister. After a threshold time has elapsed since the fuel vapor was directed to the AIS HC trap, it can be inferred that the vapor has been adsorbed by the AIS HC trap. The engine can be cranked without fuel and the intake throttle closed to direct any remaining, unadsorbed vapor from the intake manifold to the atmosphere via the exhaust passage. The intake throttle can then be opened while continuing to run the engine dry so that the ambient airflow can be used to flush the AIS HC trap. The fuel vapor from the AIS HC trap can be desorbed and directed to the exhaust passage along with the ambient airflow. The desorbed fuel vapor flowing through the exhaust passage can cause the exhaust air-fuel ratio to change from lean of stoichiometry to rich of stoichiometry. During the AIS HC trap flush, in response to the exhaust air-fuel ratio remaining lean of stoichiometry, the AIS HC trap can be diagnosed as degraded. Upon detection of AIS HC trap degradation, upon completion of immediately subsequent engine operation, the engine can be run dry to direct any remaining fuel vapor in the intake system to the exhaust catalyst via the engine cylinders.

[0008] In this way, by appropriately utilizing existing engine components, such as heated exhaust gas oxygen sensors, the need for additional sensors and / or equipment for diagnosing the AIS HC trap can be reduced or eliminated. By using the fuel pump to generate fuel vapor, diagnostics of the AIS HC trap can be performed even during engine-off conditions. The technical benefit of performing diagnostics on the AIS HC trap during engine-off conditions is that the HC trap is flushed during the diagnostic procedure, thereby limiting effluent emissions. Overall, by regularly monitoring the health of the AIS HC trap, emissions quality can be improved.

[0009] It should be understood that the above summary is provided to introduce in simplified form a selection of concepts that 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 solve any disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 An exemplary vehicle propulsion system is schematically illustrated.

[0011] Figure 2 An exemplary vehicle system having an air intake system hydrocarbon (AIS HC) trap is schematically illustrated.

[0012] Figure 3 A block diagram of an exemplary autonomous driving system is schematically shown.

[0013] Figure 4 A flow chart illustrating a diagnostic routine for diagnosing a degraded AIS HC trap is shown.

[0014] Figure 5 An exemplary diagnostic of an AIS HC trap during engine off conditions according to the present disclosure is shown. DETAILED DESCRIPTION

[0015] The following description relates to a system and method for diagnosing an air intake system hydrocarbon (AIS HC) trap. The system and method may be applied to a vehicle system that is capable of reverse-rotating the engine without fuel using an electric motor, such as a Figure 1 The engine may be coupled to a hybrid vehicle system including Figure 2 In some examples, AIS HC trap diagnostics can be performed in an autonomous vehicle, where Figure 3An exemplary autonomous vehicle control system is depicted. During a vehicle key-off condition, the vehicle's engine controller may be configured to execute an exemplary routine to indicate degradation of the AIS HC trap. In an example, Figure 4 Diagnostic procedures shown in . Figure 5 Example engine operation is shown to implement AIS HC trap diagnostics during vehicle key-off conditions.

[0016] 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, while 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 a liquid fuel (e.g., gasoline) to produce an engine output, while motor 120 can consume electrical energy to produce a motor output. Therefore, a vehicle having propulsion system 100 can be referred to as a hybrid electric vehicle (HEV).

[0017] Vehicle propulsion system 100 can utilize various different operating modes depending on the operating conditions encountered by the vehicle propulsion system. Some of these modes can enable engine 110 to be maintained in a shut-down state (i.e., set to a deactivated state) in which the engine ceases fuel combustion. For example, under selected operating conditions, when engine 110 is deactivated, motor 120 can propel the vehicle via drive wheels 130 as indicated by arrow 122.

[0018] During other operating conditions, engine 110 can be set to a deactivated state (as described above), while motor 120 can be operated to charge energy storage device 150. For example, as indicated by arrow 122, motor 120 can receive wheel torque from drive wheels 130, wherein the motor can convert the vehicle's kinetic energy into electrical energy for storage at energy storage device 150 as indicated by arrow 124. This operation can be referred to as regenerative braking of the vehicle. Thus, in some embodiments, motor 120 can provide a generator function. However, in other embodiments, generator 160 can alternatively receive wheel torque from drive wheels 130 (either directly or via motor 120), wherein the generator can convert the vehicle's kinetic energy into electrical energy for storage at energy storage device 150, as indicated by arrow 162.

[0019] During still other operating conditions, the engine 110 can be operated by combusting fuel received from the fuel system 140 as indicated by arrow 142. For example, when the motor 120 is deactivated, the engine 110 can be operated to propel the vehicle via the drive wheels 130 as indicated by arrow 112. During other operating conditions, both the engine 110 and the motor 120 can each be operated to propel the vehicle via the drive wheels 130 as indicated by arrows 112 and 122, respectively. A configuration in which both the engine and the motor can selectively propel the vehicle can be referred to as a parallel vehicle propulsion system. It should be noted that in some embodiments, the motor 120 can propel the vehicle via a first set of drive wheels, while the engine 110 can propel the vehicle via a second set of drive wheels.

[0020] In other embodiments, the 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, the engine 110 can be operated to power the motor 120, which in turn can propel the vehicle via the drive wheels 130, as indicated by arrow 122. For example, during selected operating conditions, the engine 110 can drive the generator 160 as indicated by arrow 116, which can in turn supply electrical energy to one or more of: the motor 120 as indicated by arrow 114 or the energy storage device 150 as indicated by arrow 162. As another example, the engine 110 can be operated to drive the motor 120, which can in turn provide a generator function to convert the engine output into electrical energy, where the electrical energy can be stored at the energy storage device 150 for subsequent use by the motor.

[0021] In some embodiments, motor 120 can be operated to rotate engine 110. In addition to or as an alternative to motor 120, generator 160 can also be operated to rotate engine 110. As an example, by rotating engine 110 during a cold start operation, motor 120 can act as a starter motor. Motor 120 and / or generator 160 can rotate engine 110 without providing fuel to the engine for combustion. For example, during electric-only operation, rotating the engine can allow the speed of rotating transmission components to be maintained or adjusted while adjusting the torque provided to drive wheels 130. In some cases, the engine can be rotated unfueled by the motor and / or generator to generate intake vacuum without consuming fuel. This unfueled rotation can be achieved when the motor and / or generator are used to propel the vehicle and / or when the motor and / or generator are disengaged from the drive wheels (e.g., when the vehicle is parked, at idle, or during a deceleration fuel shutoff mode). In some examples, the engine can be rotated unfueled during diagnostics of engine components such as an intake system hydrocarbon trap. Figure 4 An exemplary method utilizing unfueled engine rotation is depicted.

[0022] 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 fuels. 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. Other suitable fuels or fuel mixtures may also be supplied to engine 110, wherein they may be burned at the engine to generate engine output. The engine output may be used to propel the vehicle as indicated by arrow 112 or to recharge energy storage device 150 via motor 120 or generator 160.

[0023] In some embodiments, energy storage device 150 may be configured to store electrical energy that may be supplied to other electrical loads resident on the vehicle (in addition to the motor), including cabin heating and air conditioning, engine starting, headlights, cabin audio and video systems, etc. As non-limiting examples, energy storage device 150 may include one or more batteries and / or capacitors.

[0024] Control system 190 may communicate with one or more of engine 110, motor 120, fuel system 140, energy storage device 150, and generator 160. Figure 4 As described in the flowchart of FIG. 1 , 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. Furthermore, control system 190 may send control signals to one or more of engine 110, motor 120, fuel system 140, energy storage device 150, and generator 160 in response to the 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 pedal position sensor 193 in communication with pedal 192. Pedal 192 may illustratively represent a brake pedal and / or an accelerator pedal.

[0025] 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 a recharging operation of 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).

[0026] In other embodiments, power transmission cable 182 may be omitted, where electrical energy may be received wirelessly 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. It should be understood that any suitable method 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.

[0027] 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 embodiments, fuel tank 144 may be configured to store fuel received from fuel dispensing device 170 until it is supplied to engine 110 for combustion. In some embodiments, 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 in fuel tank 144 (e.g., as identified by the fuel level sensor) may be communicated to the vehicle operator, for example, via a fuel gauge or an indication via human-machine interface 194.

[0028] The human-machine interface 194 may include a vehicle instrument panel 195. The vehicle instrument panel 195 may include indicator lights and / or a text-based display that displays messages to the driver. In some embodiments, the vehicle instrument panel 195 may transmit audio messages to the driver with or without displaying visual messages. The vehicle instrument panel 195 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 195 may include a refueling button 196 that can be manually actuated or pressed by the vehicle driver to initiate refueling. For example, as described in more detail below, in response to the vehicle driver actuating the refueling button 196, the fuel tank in the vehicle may be depressurized so that refueling can be performed.

[0029] Figure 2 A schematic diagram of a vehicle system 206 is shown. Vehicle system 206 includes an engine system 208 coupled to an emission control system 251 and a fuel system 218. 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 Figure 1 A hybrid electric vehicle system 100 is provided.

[0030] The engine system 208 may include an engine 210 having a plurality of cylinders 230. The engine 210 may be Figure 1 110. The engine 210 includes an engine intake 223 and an engine exhaust 225. The engine intake 223 includes a throttle valve 262 fluidly coupled to an engine intake manifold 244 via an intake passage 242. The engine exhaust 225 includes an exhaust manifold 248 leading to an exhaust passage 235, which directs exhaust gas to the atmosphere. An exhaust oxygen sensor 237 can be coupled to the exhaust passage 235. The oxygen sensor 237 can be a linear oxygen sensor or UEGO (universal or wide-range exhaust oxygen), a two-state oxygen sensor or EGO, or a HEGO (heated EGO). The engine exhaust 225 can include one or more exhaust catalysts 270, which can be mounted in a close-coupled position in the exhaust port. One or more emission control devices can include a three-way catalyst, a lean NOx trap, a diesel particulate filter, an oxidation catalyst, etc. It should be understood that other components (such as various valves and sensors) can be included in the engine.

[0031] An intake system hydrocarbon trap (AIS HC) 224 can be placed in the intake manifold of engine 210 to adsorb fuel vapor emitted from unburned fuel in the intake manifold, fuel agitated from leaking injectors, and / or fuel vapor in crankcase ventilation emissions during engine shutdown periods. The AIS HC may comprise a stack of sequentially layered polymer sheets impregnated with an HC vapor adsorption / desorption material. Optionally, the adsorption / desorption material may be filled in the areas between the polymer sheet layers. The adsorption / desorption material may comprise one or more of carbon, activated carbon, zeolite, or any other HC adsorption / desorption material. When engine operation results in intake manifold vacuum and generates airflow through the AIS HC, the trapped vapors are passively desorbed from the AIS HC and combusted in the engine. Thus, during engine operation, intake fuel vapors are stored and desorbed from the AIS HC 224. Alternatively, fuel vapors stored during engine shutdown may also be desorbed from the AIS HC during engine operation. In this way, the AIS HC 224 may be continuously loaded and flushed, and the trap may reduce evaporative emissions from the intake tract even when the engine 210 is shut down.

[0032] Fuel system 218 may include a fuel tank 220 coupled to a fuel pump system 221. Fuel pump system 221 may include one or more pumps for pressurizing fuel delivered to injectors (such as the exemplary injector 266 shown) of engine 210. Although only a single injector 266 is shown, additional injectors are 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 store 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.

[0033] Vapors generated in fuel system 218 may be directed to evaporative emission control system 251, which includes fuel vapor canister 222, via vapor recovery line 231 before being purged into engine air 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 under 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.

[0034] Furthermore, in some examples, one or more fuel tank vent valves may be located 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 maintain a low pressure or vacuum without increasing the fuel evaporation rate in the fuel tank (which would otherwise occur if the fuel tank pressure were to decrease). For example, conduit 271 may include a grade vent valve (GVV) 287, conduit 273 may include a fill limit vent 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 a fuel fill system 219. In some examples, the fuel fill system may include a fuel tank cap 205 for sealing the fuel fill system from the atmosphere. Fueling system 219 is coupled to fuel tank 220 via a fuel fill pipe or neck 211.

[0035] In addition, refueling system 219 may include a refueling lock 245. In some embodiments, refueling lock 245 may be a fuel tank cap locking mechanism. The fuel tank cap locking mechanism may be configured to automatically lock the fuel tank cap in a closed position so that the fuel tank cap cannot be opened. For example, when the pressure or vacuum in the fuel tank is greater than a threshold value, fuel tank cap 205 may remain locked via refueling lock 245. In response to a refueling request, such as a request initiated by the vehicle driver, the fuel tank may be depressurized, and the fuel tank cap may be unlocked after the pressure or vacuum in the fuel tank drops below a threshold value. The fuel tank cap locking mechanism may be a latch or a clutch that prevents removal of the fuel tank cap when engaged. The latch or clutch may be electrically locked, for example, by a solenoid, or mechanically locked, for example, by a pressure diaphragm.

[0036] In some embodiments, refuel lock 245 may be a filler pipe valve located at the mouth of fuel filler pipe 211. In such embodiments, refuel lock 245 may not prevent removal of fuel tank cap 205. Instead, refuel lock 245 may prevent insertion of a refueling pump into fuel filler pipe 211. The filler pipe valve may be electrically locked, for example, by a solenoid, or mechanically locked, for example, by a pressure diaphragm.

[0037] In some embodiments, fuel lock 245 can be a fuel door lock, such as a latch or clutch that locks a fuel door located in a body panel of the vehicle. The fuel door lock can be locked electrically, such as by a solenoid, or mechanically, such as by a pressure diaphragm.

[0038] In embodiments where an electrical mechanism is used to lock refuel lock 245, for example, when the fuel tank pressure drops below a pressure threshold, refuel lock 245 may be unlocked by a command from controller 212. In embodiments where a mechanical mechanism is used to lock refuel lock 245, for example, when the fuel tank pressure drops to atmospheric pressure, refuel lock 245 may be unlocked via a pressure gradient.

[0039] Emission control system 251 may include one or more emission control devices, such as one or more fuel vapor canisters 222 filled with a suitable adsorbent that is configured to temporarily capture fuel vapors (including vaporized hydrocarbons) during fuel tank refill operations, as well as "running losses" (i.e., fuel that vaporizes during vehicle operation). In one example, the adsorbent used is activated carbon. Emission control system 251 may also include a canister vent path or vent line 227 that vents gases from canister 222 to the atmosphere while storing or capturing fuel vapors from fuel system 218.

[0040] Canister 222 may include a buffer 222a (or a buffer zone), each of which includes an adsorbent. As shown, the volume of buffer 222a may be smaller than the volume of canister 222 (e.g., a fraction of the volume). The adsorbent in buffer 222a may be the same as or different from the adsorbent in the canister (e.g., both may include charcoal). Buffer 222a may be positioned within canister 222 such that during canister loading, fuel tank vapors are first adsorbed within the buffer, and then, when the buffer is saturated, additional fuel tank vapors are adsorbed within the canister. In contrast, during canister flushing, fuel vapors are first desorbed from the canister (e.g., until a threshold amount is reached) and then from the buffer. In other words, the loading and unloading of the buffer is not linear with the loading and unloading of the canister. Therefore, the effect of the canister buffer is to suppress any fuel vapor spikes flowing from the fuel tank to the canister, thereby reducing the likelihood of any fuel vapor spikes entering the engine. One or more temperature sensors 232 may be coupled to canister 222 and / or within the canister. When fuel vapor is adsorbed by the adsorbent in the canister, heat (adsorption heat) is generated. Similarly, when fuel vapor is desorbed from the adsorbent in the canister, heat is dissipated. In this way, the adsorption and desorption of fuel vapor by the canister can be monitored and estimated based on temperature changes within the canister.

[0041] Vent line 227 may also allow fresh air to be drawn into canister 222 when stored fuel vapors are flushed from fuel system 218 to engine air 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 so that vacuum from engine intake manifold 244 is provided to the fuel vapor canister for flushing. In some examples, vent line 227 may include air filter 259 positioned upstream of canister 222.

[0042] In some examples, the flow of air and vapors between canister 222 and the atmosphere can be regulated by a canister vent valve 297 coupled within vent line 227. When included, the canister vent valve can be a normally open valve, allowing fuel tank isolation valve 252 (FTIV) to control venting of fuel tank 220 from the atmosphere. FTIV 252 can be located between the fuel tank and the fuel vapor canister within conduit 278. FTIV 252 can be a normally closed valve that, when open, allows fuel vapors to vent from fuel tank 220 to canister 222. The fuel vapors can then be vented to the atmosphere or flushed to engine air intake 223 via canister flush valve 261.

[0043] By selectively adjusting various valves and solenoids, fuel system 218 may be operated in a variety of modes by controller 212. For example, the fuel system may be operated in a fuel vapor storage mode (e.g., during a fuel tank refueling operation and with the engine not running), wherein controller 212 may open isolation valve 252 while closing canister purge valve (CPV) 261 to direct refueling vapors directly into canister 222 while preventing fuel vapors from being directed into the intake manifold.

[0044] 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 while keeping canister purge valve 261 closed to depressurize the fuel tank before allowing refueling to be performed. Thus, isolation valve 252 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.

[0045] 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 running), in which controller 212 can open canister purge valve 261 while closing isolation valve 252. Here, vacuum generated by the intake manifold of the operating engine can be used to draw fresh air through vent 227 and through fuel vapor canister 222 to purge stored fuel vapor into intake manifold 244. In this mode, fuel vapors purged from the canister are combusted in the engine. Purging can continue until the amount of fuel vapor stored in the canister is below a threshold.

[0046] During vehicle key-off conditions, fuel system 218 and evaporative emission control system 251 can be used, as appropriate, to diagnose engine components such as AIS HC trap 224. Fuel tank 220 can be isolated by actuating FTIV 252 to a closed position, and fuel vapor can be generated by operating fuel pump 221 coupled to fuel tank 220. Vapor pressure in the fuel tank can be estimated via fuel tank pressure sensor 291 coupled to fuel tank 220, and in response to the vapor pressure increasing above a threshold pressure, each of throttle 262 and CVV 297 can be closed, each of FTIV 252 and CPV 261 can be opened, and fuel vapor can be directed from fuel tank 220 to engine intake manifold 244. While directing fuel vapor to the adsorbent material in AIS HC trap 224, the fuel vapor may be allowed to reside in the engine intake for a threshold duration, and after the threshold duration, the engine may be cranked without fuel with throttle 262 closed until the exhaust air-fuel ratio estimated via oxygen sensor 237 is lean of stoichiometry, after which throttle 262 may be actuated to a wide-open position. An indication of the presence of degradation of AIS HC trap 224 may be responsive to the exhaust air-fuel ratio changing from lean of stoichiometry to rich of stoichiometry when throttle 262 is opened while the engine is cranked without fuel. An indication of the absence of degradation of AIS HC trap 224 may be responsive to the exhaust air-fuel ratio remaining lean of stoichiometry when throttle 262 is opened while the engine is cranked without fuel.

[0047] Controller 212 may include part of a control system 214. Control system 214 is shown 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, sensors 216 may include exhaust gas sensor 237 located upstream of an emission control device, temperature sensor 233, fuel tank pressure sensor (pressure sensor) 291, and canister temperature sensor 232. Other sensors, such as pressure, temperature, air-fuel ratio, and composition sensors, may be coupled to various locations within vehicle system 206. As another example, actuators may include intake throttle 262, fuel pump 221, fuel tank isolation valve 253, canister purge valve 261, and canister vent valve 297. Control system 214 may include controller 212. The controller may receive input data from the various sensors, process the input data, and trigger actuators in response to the processed input data based on instructions corresponding to one or more routines or code programmed into the instructions. In one example, during AIS HC trap 224 diagnostics, controller 212 may send a signal to fuel pump 221 to operate pump 221 to generate fuel vapor in fuel tank 220. The controller may then actuate FTIV 252 to an open position to direct fuel vapor to AIS HC trap 224. The controller may cause engine 210 to operate via an electric motor such as Figure 1 The motor 120 is rotated to flush the AIS HC trap 224 and monitor the change of the exhaust gas air-fuel ratio via the oxygen sensor 237.

[0048] In some examples, the controller can 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 a corresponding awake mode. For example, the controller can be placed in sleep mode after a vehicle shutdown event to perform diagnostic routines for a period of time after the vehicle shutdown event. The controller can have a wake-up input that allows the controller to return to awake mode based on input received from one or more sensors. For example, the opening of a vehicle door can trigger a return to awake mode. For example, the wake-up function can enable circuitry to wake the controller to perform diagnostics of the AIS HC trap 224 in a timely manner.

[0049] The diagnostic routine for the AIS HC trap 224 may be performed in a vehicle configured as an autonomous vehicle, and exemplary autonomous driving systems are referenced below. Figure 3 Have a discussion. Figure 3 It can be operated on Figure 1. As shown, the autonomous driving system 300 includes a user interface device 310, a navigation system 315, at least one autonomous driving sensor 320, and an autonomous mode controller 325.

[0050] The user interface device 310 may be configured to present information to a vehicle occupant in situations where a vehicle occupant may be present. However, it will be appreciated that in certain situations, the vehicle may operate autonomously without the presence of a vehicle occupant.

[0051] The information presented may include audible information or visual information. In addition, the user interface device 310 may be configured to receive user input. Therefore, the user interface device 310 may be located in a passenger compartment (not shown) of a vehicle. In some possible approaches, the user interface device 310 may include a touch-sensitive display screen.

[0052] The navigation system 315 can be configured to determine the current location of the vehicle using, for example, a global positioning system (GPS) receiver configured to triangulate the vehicle's position relative to satellites or terrestrial transmission towers. The navigation system 315 can also be configured to form a route from the current location to a selected destination and display a map and present driving directions to the selected destination via, for example, the user interface device 310.

[0053] The autonomous driving sensors 320 may include any number of devices configured to generate signals to assist in navigating the vehicle. Examples of the autonomous driving sensors 320 may include radar sensors, lidar sensors, vision sensors (e.g., cameras), vehicle-to-vehicle infrastructure networks, and the like. The autonomous driving sensors 320 may enable the vehicle to "see" the road and the vehicle's surroundings, and / or navigate various obstacles when the vehicle system 100 is operating in autonomous mode. The autonomous driving sensors 320 may be configured to output sensor signals to, for example, an autonomous mode controller 325.

[0054] The autonomous mode controller 325 can be configured to control one or more subsystems 330 when the vehicle is operating in autonomous mode. Examples of subsystems 330 that can be controlled by the autonomous mode controller 325 include a braking subsystem, a suspension subsystem, a steering subsystem, and a powertrain subsystem. The autonomous mode controller 325 can control any one or more of these subsystems 330 by outputting signals to control units associated with the subsystems 330. In one example, the braking subsystem can include an anti-lock braking subsystem configured to apply braking force to one or more wheels. As discussed herein, applying braking force to one or more wheels may be referred to as activating the brakes. To autonomously control the vehicle, the autonomous mode controller 325 can output appropriate commands to the subsystems 330. The commands can cause the subsystems to operate according to driving characteristics associated with the selected driving mode. For example, driving characteristics can include how aggressively the vehicle accelerates and decelerates, how much space the vehicle leaves behind the vehicle ahead, how often the autonomous vehicle changes lanes, and so on.

[0055] In this way, Figures 1 to 3 A system is implemented by components, the system including: a vehicle, including an autonomous vehicle and / or a hybrid vehicle; an electric machine; an engine, including an intake passage and an exhaust passage; an intake throttle valve, coupled to the intake passage; a fuel vapor canister, selectively coupled to the engine intake passage via a canister purge valve (CPV); a fuel tank, which supplies fuel to the engine, the fuel tank selectively coupled to the fuel vapor canister via a fuel tank isolation valve (FTIV); a fuel pump, housed in the fuel tank; an air intake system hydrocarbon (AIS HC) trap, located in the engine intake passage; a heated exhaust gas oxygen (HEGO) sensor, coupled to the exhaust passage; and a controller having computer-readable instructions stored on a non-transitory memory, the computer-readable instructions, when executed during an engine shut-off condition, causing the controller to: isolate the fuel tank by closing the FTIV and operate the fuel pump to generate fuel vapor, and direct the generated fuel vapor to the AIS by opening the FTIV and the CPV. HC trap, cranking the engine without fuel via the electric machine and opening the throttle to a wide-open position after stopping directing fuel vapor to the AISHC trap, and indicating degradation of the AISHC trap in response to an exhaust air-fuel ratio being lean of a stoichiometric air-fuel ratio.

[0056] Figure 4 An exemplary method 400 is shown that may be implemented to clean an intake system hydrocarbon (AIS HC) trap (such as an Figure 2The AIS HC trap 224) can be used to perform diagnostics. The controller can be based on instructions stored in the memory of the controller and combined with sensors from the engine system (such as those referenced above). Figure 2 The controller may use signals received from sensors (described in the accompanying drawings) to execute instructions for performing method 400 and the remaining methods included herein. According to the methods described below, the controller may employ engine actuators of the engine system to adjust engine operation.

[0057] At 402, the method includes determining whether conditions for initiating an AIS HC trap diagnostic are met. In one example, the conditions for initiating an AIS HC trap diagnostic may include a vehicle-off condition when the vehicle is unoccupied (no occupants present in the vehicle). Seat load cells, onboard cameras, and / or door sensing technology may be used to ensure the vehicle is unoccupied. In another example, the AIS HC trap diagnostic may be performed during autonomous vehicle mode when the vehicle is operating without a driver and when the vehicle is not being propelled by engine torque. Vehicle operation may be controlled from a remote location or may be pre-programmed in controller memory. During vehicle operation in autonomous mode, the diagnostic may be opportunely performed when the vehicle is stopped at a traffic signal or immediately after completing a drive cycle. In yet another example, the AIS HC trap diagnostic may be performed in response to the controller waking up after a predetermined duration following a key-off event. Conditions for initiating an AIS HC trap diagnostic include confirming that engine sensors, such as an exhaust gas oxygen sensor, are not degraded and generally that no diagnostic codes (flags) are set indicating degradation of any engine components. Furthermore, before initiating an AIS HC trap diagnostic, the controller may verify whether a predetermined duration has elapsed since the execution of an existing AIS HC trap diagnostic routine. In some examples, such a predetermined duration may include one day, greater than one day but less than two days, greater than two days, etc. In other examples, the predetermined duration may include miles driven, vehicle operating hours, or other parameters.

[0058] If it is determined that the conditions for initiating an AIS HC trap diagnostic are not met, then at 404, the AIS HC trap diagnostic routine may be postponed until the conditions are met. In some examples, if the AIS HC trap diagnostic conditions are not met, then the current operating parameters may be continued until the AIS HC trap diagnostic conditions are met. Such operating parameters may include if the vehicle is operating with fuel delivered from a fuel tank to one or more engine cylinders via fuel injectors of a fuel system and combustion of air and fuel performed in the cylinders. Hydrocarbons ejected by any leaks in the injectors and / or fuel agitation in the engine intake manifold may be adsorbed by the AIS HC trap. A fuel tank isolation valve (such as a vent valve) located within a conduit between the fuel tank and the fuel vapor canister may be provided. Figure 2 The FTIV 252 in the canister can be maintained in a closed position. A canister purge valve (such as a canister purge valve) located in a purge line connecting the fuel vapor canister to the engine intake manifold Figure 2 A canister vent valve (such as CPV 262 in FIG. 1 ) located in a vent line connecting the fuel vapor canister to the atmosphere may be maintained in a closed position. Figure 2 The CVV 297 in the engine can be maintained in an open position. The engine torque generated by combustion in the engine cylinders can be used to propel the vehicle.

[0059] If it is determined that the conditions for initiating the AIS HC trap diagnostic are met, then at 406, the routine includes spinning or rotating the engine at a predetermined speed (e.g., a predetermined RPM) without fuel. Spinning the engine without fuel can cause any unburned and unadsorbed fuel vapors present in the engine intake system and engine cylinders to be directed to the atmosphere via the exhaust passage. Due to the lower pressure created in the intake manifold by the engine spinning, ambient air can enter the engine intake manifold via the intake throttle and flow to the exhaust passage, entraining HC vapors. Spinning the engine without fuel can include spinning the engine via a motor (such as Figure 1 The motor 120 in the vehicle is rotated, wherein the motor can be driven by an onboard battery (such as Figure 1 The energy storage device 150 in the engine is powered. In a non-hybrid vehicle, the engine can be rotated via the vehicle's starter motor and battery. The engine speed can be controlled to a predetermined speed via the motor. The predetermined engine speed may include a speed that regenerates a strong airflow through the engine intake manifold and engine cylinders, which can remove any HC vapors while the engine is rotating. In one example, the predetermined speed may be less than 500 rpm.

[0060] When HC vapor is directed to the atmosphere through the exhaust passage, the HC vapor flows with the ambient air past an exhaust gas oxygen sensor such as Figure 2 At 408, the exhaust air-fuel ratio (AFR) may be estimated via a heated exhaust gas oxygen (HEGO) sensor. Due to the presence of HC vapors in the airflow through the HEGO sensor, the exhaust AFR may be estimated to be richer than stoichiometric. Stoichiometric AFR represents a 1:1 air-fuel ratio, and richer than stoichiometric AFR represents a higher fraction of fuel (vapor) compared to air.

[0061] At 410, the routine includes determining whether the AFR estimated by the HEGO sensor is lean of stoichiometric. Lean of stoichiometric AFR indicates a higher fraction of air compared to fuel. Once the entire volume of unburned and unadsorbed HC vapors is directed to the atmosphere via the exhaust passage, ambient air (without HC vapors present) can flow through the HEGO sensor when the engine is running without fuel. Therefore, an AFR rich of stoichiometry due to the presence of HC vapors in the exhaust gas flow may become lean of stoichiometric AFR.

[0062] If it is determined that the AFR estimated by the HEGO sensor is not lean of stoichiometric, it can be inferred that HC vapors are present in the exhaust gas flow, causing the AFR to remain rich of stoichiometric. Rich of stoichiometric AFR indicates a higher fuel fraction relative to air. At 411, the engine continues to rotate, allowing air to continue flowing from the intake manifold to the exhaust tract via the engine cylinders, entraining HC vapors until the entire volume of trapped vapors is removed. If it is determined that the AFR is lean of stoichiometric, it can be inferred that the entire volume of trapped HC vapors from the engine intake manifold and cylinders has been removed to the atmosphere, and ambient air (free of HC vapors) is flowing through the exhaust tract. Once the trapped HC vapors are removed from the engine system, at 412, the controller can signal the motor to stop the engine. In this way, by removing all trapped hydrocarbons from the engine cylinders (confirmed by the lean of stoichiometric exhaust AFR), it can be ensured that HC trapped in the engine cylinders and intake manifold will not affect the AIS HC trap diagnostic.

[0063] At 414, the controller may signal an actuator coupled to the FTIV to close the FTIV. Because the engine is in a non-combustion state during the AIS HC trap diagnostic, the FTIV may be in an open position to allow fuel vapors generated in the fuel tank to flow to the vapor canister, where the vapors can be adsorbed. If the FTIV is in a closed position, the FTIV position may be maintained closed. By closing the FTIV valve, the fuel tank may be isolated from the fuel vapor canister and the engine intake manifold.

[0064] At 416 , a fuel pump (such as Figure 2 The controller may activate fuel pump 221 in the fuel tank to generate vapor in the fuel tank. The controller may send a signal to an actuator coupled to the fuel pump to activate the pump. When the fuel pump operates, the fuel in the fuel tank may be agitated, causing the fuel to vaporize, thereby forming fuel vapor in the fuel tank. Because the FTIV is closed, the fuel tank is isolated from the rest of the engine components, and fuel vapor may not escape from the fuel tank, thereby increasing fuel tank pressure.

[0065] At 417 , the routine includes determining a fuel tank pressure via a fuel tank pressure sensor (such as Figure 2 The controller determines whether the fuel tank pressure estimated by the FTPT (291) in the AIS HC trap is above a threshold pressure. The threshold pressure may correspond to a volume of fuel vapor that, if directed to the AIS HC trap, would saturate the trap. The threshold pressure may be calibrated based on the adsorption capacity of the AIS HC trap. In one example, the threshold pressure may be 6 inches of water column. If the fuel tank pressure is determined to be below the threshold pressure, then at 418, the fuel pump may continue to operate to generate fuel vapor. If the fuel tank pressure is determined to be above the threshold pressure, it may be inferred that the desired amount of fuel vapor to saturate the AIS HC trap has been generated, and further generation of fuel vapor is undesirable. At 419, the controller may send a signal to an actuator coupled to the fuel pump to cease operation of the fuel pump.

[0066] At 420, the controller may send a signal to each of the actuator coupled to the FTIV and the actuator coupled to the CPV to open the FTIV and the CPV, respectively. By opening the FTIV and the CPV, fuel vapors generated in the fuel tank may be directed from the fuel tank to the engine intake manifold via the fuel vapor canister and the purge line. The controller may send a signal to the actuator coupled to the CVV to actuate the CVV to a closed position. When the CVV is closed, fuel vapors may not escape into the atmosphere via the vent line. A smaller portion of the fuel vapors may be adsorbed by the fuel vapor canister, while the remaining larger portion of the fuel vapors may be directed to the engine intake manifold. When the FTIV and CPV are opened and the CVV is closed, a timer may be started. The timer records the duration that has elapsed since the initiation of the fuel vapor directing from the fuel tank to the intake manifold.

[0067] At 421, the routine includes determining whether the time elapsed since the initiation of fuel vapor induction is greater than a threshold duration. The threshold duration may be calibrated based on the time required for the entire volume of fuel vapor to flow from the fuel tank to the intake manifold and be adsorbed by the AIS HC trap. In one example, the threshold duration may be 30 seconds. If the elapsed time is determined to be less than the threshold duration, it may be inferred that additional time may be required for the AISHC trap to adsorb fuel vapor and maintain current engine conditions.

[0068] If it is determined that the time elapsed since the initiation of fuel vapor routing is greater than a threshold duration, it can be inferred that the fuel vapor routed from the fuel tank may be adsorbed by the AIS HC trap. In this way, by actuating the FTIV to a closed position, operating a fuel pump coupled to the fuel tank until the fuel vapor pressure in the fuel tank increases to a threshold pressure, and then routing fuel vapor from the fuel tank to the AIS HC trap, the trap may become saturated with hydrocarbons.

[0069] At 424, the intake throttle can be actuated to a fully closed position so that ambient air can enter the engine intake manifold without passing through the intake throttle. At 426, the controller can send a signal to the motor to rotate the engine without fuel at a predetermined engine speed. As the engine rotates, any unadsorbed fuel vapors remaining in the engine intake manifold can be directed to the engine exhaust manifold via the engine cylinders. At 428, the exhaust air-fuel ratio (AFR) can be estimated via a HEGO sensor housed in the exhaust tract. When fuel vapors flow through the HEGO, the exhaust AFR can be estimated by the HEGO sensor as richer than stoichiometric.

[0070] At 430, the routine includes determining whether the AFR estimated by the HEGO sensor is lean of stoichiometric. Once the entire volume of unadsorbed HC vapors is directed to the atmosphere via the exhaust passage, the remaining air in the engine system (without HC vapors present) can flow via the HEGO sensor when the engine is running without fuel. Therefore, an AFR rich in stoichiometry due to the presence of HC vapors in the exhaust gas flow may become lean of stoichiometric.

[0071] If it is determined that the AFR estimated by the HEGO sensor is not lean of stoichiometric, it can be inferred that HC vapors are present in the exhaust gas flow, causing the AFR to remain rich of stoichiometric. At 432, the engine continues to rotate with the throttle closed to remove unadsorbed HC vapors. If it is determined that the AFR is lean of stoichiometric, it can be inferred that the entire volume of trapped HC vapors from the engine intake manifold has been removed to the atmosphere and that air (free of HC vapors) is flowing through the exhaust tract. Once the HEGO sensor reading becomes lean of stoichiometric, at 434, the controller can send a signal to the throttle plate to fully open the intake throttle (to a wide-open throttle position), thereby allowing ambient air to flow into the engine intake manifold via the intake throttle. In addition, the controller can send a signal to an actuator coupled to the CPV to actuate the CPV to a fully closed position. By closing the CPV and maintaining the fuel pump in an inactive condition, any additional fuel vapors directed from the fuel tank to the intake manifold can be stopped.

[0072] As the engine rotates, as ambient air flows through the engine intake manifold housing the AIS HC trap, intake manifold pressure can then stimulate desorption of hydrocarbons from the AIS HC trap. Ambient airflow from the intake throttle can direct the desorbed HC to the atmosphere via the exhaust manifold.

[0073] At 436, the exhaust air-fuel ratio (AFR) can be estimated via a HEGO sensor housed in the exhaust passage. At 438, the routine includes determining whether the exhaust AFR has changed from lean of stoichiometry to rich of stoichiometry. As HC flows through the HEGO sensor housed in the exhaust passage, the exhaust AFR estimated by the HEGO sensor can change from lean of stoichiometry to rich of stoichiometry. If it is determined that the exhaust AFR has changed from lean of stoichiometry to rich of stoichiometry, it can be inferred that the AIS HC trap is capable of adsorbing HC (fuel vapor) and also desorbing HC when ambient air flows through the HC trap under intake manifold pressure conditions. In this way, the AIS HC trap can be actively flushed by cranking the engine without fuel and actuating the throttle to a wide-open position to allow ambient air to flow through the AIS HC trap to the engine exhaust manifold. By removing all undesorbed fuel vapor from the engine system (as confirmed by a lean-to-stoichiometric exhaust AFR) before desorbing HC from the HC trap, it is ensured that a rich-to-stoichiometric exhaust AFR is caused by HC flowing from the AIS HC trap to the atmosphere through the exhaust passage (rather than from undiffused fuel vapor). At 440 , the routine includes indicating that the AIS HC trap is not degraded.

[0074] However, if it is determined that the exhaust AFR will not become richer than the stoichiometric AFR even if ambient air is directed through the AIS HC trap, it can be inferred that HC will not be desorbed from the AIS HC trap. In one example, the HC trap may be unable to adsorb fuel vapors when fuel vapors from the fuel tank are directed to the HC trap. At 442, a diagnostic code (flag) indicating degradation of the AIS HC trap may be set.

[0075] Because the AIS HC trap is degraded, engine operation during subsequent engine cycles may be adjusted at 444 . In one example, at the completion of the drive cycle, the engine may be run without fuel to direct any remaining fuel vapors in the intake system via the engine cylinders to the exhaust catalyst. The vapors may be processed in the catalyst. If fuel vapors remain in the engine cylinders, they may be combusted during subsequent engine cycles. In this way, fuel vapors may be removed from the intake system during AISHC trap degraded conditions.

[0076] After the entire volume of desorbed HC flows through the exhaust passage, the HEGO sensor reading may change from rich to lean of stoichiometric AFR. At 446, the diagnostic routine is complete and the engine may no longer rotate. The controller may send a signal to the motor powering the engine to stop the engine from rotating, and the vehicle may return to a key-off condition. In one example, during a vehicle key-off condition, the FTIV may remain in an open position, the CVV may remain in an open position, and the CPV may remain in a closed position.

[0077] In this way, during engine-off conditions, an air intake system hydrocarbon (AIS HC) trap coupled to the intake manifold of the engine may be saturated by selectively directing fuel vapors from a fuel tank to the intake manifold, the directing of fuel vapors to the intake manifold may be stopped, and the AIS HC trap may then be actively purged. During active purging of the AIS HC trap, degradation of the AIS HC trap may be indicated in response to an air-fuel ratio in an exhaust system of the engine being lean of stoichiometry.

[0078] Figure 5 An exemplary timeline 500 is shown illustrating the operation of an air intake system hydrocarbon (AIS HC) trap (such as an AIS HC) trap coupled to an engine intake manifold. Figure 2 The horizontal (x-axis) represents time, and the vertical markers t0 to t7 represent important times in the procedure for diagnosing the AIS HC trap.

[0079] The first graph (line 502) shows the change in engine speed over time. The engine can be rotated by burning air and fuel in the engine cylinders or by operating an electric motor coupled to a hybrid electric vehicle (HEV). The second graph (line 504) shows the operation of the HEV electric motor. The third graph (line 506) shows the operation of a canister vent valve (such as a vent valve) housed in a vent line coupling the fuel vapor canister to the atmosphere. Figure 2 The fourth graph (line 507) shows the position of a canister purge valve (such as CVV 297) contained in a purge line coupling the fuel vapor canister to the engine intake manifold. Figure 2 The fifth graph (line 508) shows the position of a fuel tank isolation valve (such as CPV 262) contained in a conduit coupling the fuel tank to the fuel vapor canister. Figure 2 The sixth graph (line 510) shows the position of the FTIV 252 in the fuel tank via a fuel tank pressure sensor such as Figure 2The fuel tank pressure is estimated by the FTPT 291 in FIG. 509. Dashed line 509 shows a threshold fuel tank pressure above which the amount of fuel vapor generated in the fuel tank is sufficient to saturate the AIS HC trap. The seventh graph (line 512) shows the fuel tank pressure estimated by an oxygen sensor (such as an oxygen sensor) coupled to the exhaust passage. Figure 2 2 . The exhaust gas air-fuel ratio (AFR) is estimated by oxygen sensor 237 in FIG. Dashed line 511 shows the stoichiometric exhaust gas AFR (1:1 air-fuel ratio). An eighth graph (line 514) shows the position of a throttle valve coupled to the engine intake manifold. A ninth graph (line 516) shows the operation of a fuel pump coupled to the fuel tank. A tenth graph (line 518) shows the position of a diagnostic flag indicating degradation of the AIS HC trap.

[0080] Prior to time t1, the engine is driven by combustion and rotates for vehicle propulsion. The HEV machine is not operated for engine rotation or vehicle propulsion. The intake throttle is partially open in proportion to the torque demand. The fuel pump operates to supply fuel from the fuel tank to the engine cylinders via the fuel injectors. The FTPT estimates the fuel tank pressure developed due to vaporization of fuel in the fuel tank when the fuel pump operates. The average exhaust air-fuel ratio maintains stoichiometry with fluctuating AFR between rich and lean of stoichiometry. The CPV and FTIV are maintained in the closed position, isolating the fuel tank and fuel vapor filter canister from the intake manifold, while the CVV can be maintained in the open position. Because diagnosis is not performed on the AIS HC trap, the flag is maintained in the closed position.

[0081] At time t1, the engine is shut down by suspending operation of the fuel pump and also disabling spark in the engine cylinders. The controller sends a signal to the FTIV to actuate it to the open position, directing any fuel vapors from the fuel tank to the fuel vapor canister. Between times t1 and t2, the engine remains in a shut-down condition. As fuel vapors are removed from the fuel tank, the fuel tank pressure decreases.

[0082] At time t2, after a threshold duration has elapsed since engine shutdown at time t1, a diagnosis of the AIS HC trap is initiated by waking up the controller. The controller sends a signal to the HEV engine to rotate the engine at a first engine speed without fuel. As the engine rotates, any unburned and unadsorbed (residual) fuel vapors present in the engine intake system and engine cylinders are directed to the atmosphere via the exhaust passages. Due to the lower pressure created in the intake manifold by engine rotation, ambient air can enter the engine intake manifold via the partially open intake throttle and flow to the exhaust passages, entraining fuel vapors. Between times t2 and t3, while fuel vapors flow through the exhaust passages, the exhaust AFR is estimated to be rich of stoichiometry.

[0083] At time t3, in response to the exhaust AFR changing from rich to lean, it is inferred that residual fuel vapor has been removed from the engine system by the exhaust manifold. The controller sends a signal to the HEV engine to pause engine rotation. The controller sends a signal to the fuel pump to activate the fuel pump. The fuel tank is isolated by actuating the FTIV to the closed position. Between time t3 and t4, when the fuel pump operates in the isolated fuel tank, fuel vapor is generated. The operating speed of the fuel pump for fuel vapor generation is higher than the operating speed of the fuel pump for supplying fuel to the fuel injectors (such as before time t1). As fuel vapor is generated, the fuel tank pressure increases.

[0084] At time t4, in response to the fuel tank pressure increasing above a threshold pressure 509, it is inferred that sufficient fuel vapor has been generated in the fuel tank to saturate the AIS HC trap. Threshold pressure 509 is calibrated by the controller based on the adsorption capacity of the AIS HC trap. In response to the fuel tank pressure increasing above threshold 509, the controller sends a signal to the fuel pump to suspend operation of the fuel pump. The controller sends a signal to each of the actuators coupled to the CPV and the FTIV to open the corresponding valves (CPV and FTIV). The controller also sends a signal to the actuator coupled to the CVV to close the CVV. By opening the FTIV and CPV, fuel vapor generated in the fuel tank is directed to the intake manifold via the fuel vapor canister and the canister purge line. When the CVV is closed, the vapor cannot escape to the atmosphere via the canister vent line. Between times t4 and t5, as fuel vapor flows from the fuel tank to the engine intake manifold, the fuel tank pressure decreases. Upon reaching the intake manifold, the fuel vapor is adsorbed by the AIS HC trap.

[0085] At time t5, it is inferred that the AIS HC trap has been adsorbing fuel vapor for a threshold duration. The controller signals the HEV engine to rotate the engine at a predetermined speed. The controller also signals the throttle plate to fully close the throttle. With the engine rotating and the throttle closed, ambient air does not enter the engine intake manifold through the intake throttle, and therefore, there is no air to desorb the fuel vapor adsorbed on the AIS HC trap. Between times t5 and t6, unadsorbed fuel vapor remaining in the intake manifold is directed to the atmosphere via the engine cylinders and exhaust passages. As fuel vapor flows through the exhaust passages, the AFR estimated by the exhaust oxygen sensor is richer than the stoichiometric AFR.

[0086] At time t6, in response to the AFR changing from rich to lean of stoichiometry, it is inferred that the entire volume of unadsorbed fuel vapor has escaped from the exhaust passage to the atmosphere. The controller sends a signal to the throttle plate to fully open the throttle. As the engine rotates, the throttle is actuated to the fully open position, allowing ambient air to enter the engine intake manifold. Furthermore, the controller sends a signal to the actuator coupled to the CPV to close the CPV. Between times t6 and t7, as ambient air flows under pressure through the AIS HC trap, adsorbed hydrocarbons are desorbed and directed to the atmosphere via the exhaust passage. When the CPV is closed, the desorbed hydrocarbons cannot enter the purge line. Due to the presence of desorbed hydrocarbons in the exhaust flow, the exhaust AFR changes from lean to rich of stoichiometry. Based on the change in AFR to rich of stoichiometry, it is inferred that the AIS HC trap is operating optimally and is able to adsorb and desorb hydrocarbons. Because the AIS HC trap has not degraded, the flag remains closed.

[0087] At time t7, in response to the AFR changing from rich to lean, it is concluded that the entire volume of desorbed hydrocarbons has been directed to the atmosphere and the diagnostic routine is complete. The controller sends a signal to the HEV motor to stop the engine. The intake throttle is actuated to the throttle position prior to initiation of the diagnostic routine (e.g., prior to time t2). After time t7, no engine torque and / or machine torque is used to propel the vehicle, and the engine remains in an off condition until a subsequent vehicle key is turned on.

[0088] However, between t6 and t7, even though ambient air is directed through the AIS HC trap, if the observed AFR remains leaner than the stoichiometric AFR (as indicated by dashed line 513), it can be inferred that the AIS HC trap is not flushing as desired. The lack of hydrocarbons in the exhaust gas stream may also indicate that the AIS HC trap is not adsorbing fuel vapors between times t4 and t5. Therefore, between times t6 and t7, as indicated by dashed line 518, a flag indicating degradation of the AIS HC trap will be set.

[0089] In this way, existing engine components, such as the exhaust gas oxygen sensor, can be used to diagnose the AIS HC trap. The technical benefit of using generated fuel vapor to perform diagnostics is that diagnostic procedures can be performed periodically during engine shutdown conditions, without having to wait for suitable engine operating conditions. Overall, by regularly monitoring the health of the AIS HC trap, effluent emissions can be reduced.

[0090] An exemplary engine method includes, during an unfueled engine crank start, testing for degradation of an adsorbent material located in an air intake of the engine by directing fuel vapor to the adsorbent material with a throttle valve coupled to the engine air intake in a closed position and indicating the presence or absence of adsorbent material degradation based on air-fuel ratio conditions in an exhaust system of the engine when the throttle valve is opened. In any of the foregoing examples, additionally or alternatively, the adsorbent material located in the engine air intake comprises an air intake system hydrocarbon (AIS HC) trap coupled to the engine air intake downstream of the throttle valve, and wherein the adsorbent material comprises one or more of carbon, activated carbon, or zeolite. In any or all of the foregoing examples, additionally or alternatively, the fuel vapor is directed to the adsorbent from an evaporative emission control system coupled to a fuel tank, and wherein the fuel vapor is generated by operating a fuel pump coupled to the fuel tank, the method further comprising isolating the fuel tank by actuating a fuel tank isolation valve (FTIV) contained in a conduit coupling the fuel tank to a vapor canister of the evaporative emission control system to a closed position before generating the fuel vapor. In any or all of the foregoing examples, additionally or alternatively, the method further comprises, prior to generating the fuel vapor, cranking the engine without fuel until the exhaust air-fuel ratio is lean of stoichiometry. In any or all of the foregoing examples, additionally or alternatively, directing fuel vapor to the adsorbent material includes: estimating vapor pressure in the fuel tank via a fuel tank pressure sensor coupled to the fuel tank, and in response to the vapor pressure increasing above a threshold pressure, closing the throttle, opening the FTIV, opening a canister purge valve (CPV) contained in a passage coupling the vapor canister to the engine intake, closing a canister vent valve (CVV) contained in a passage coupling the vapor canister to atmosphere, and directing fuel vapor from the fuel tank to the engine intake. In any or all of the foregoing examples, additionally or alternatively, the method further includes, while directing the fuel vapor to the adsorbent material, allowing the fuel vapor to reside in the engine intake for a threshold duration, and, after the threshold duration, cranking the engine without fuel with the throttle closed until the exhaust air-fuel ratio is lean of stoichiometric, and then opening the throttle to a wide-open position. In any or all of the foregoing examples, additionally or alternatively, the indication that degradation of the adsorbent material exists is responsive to the exhaust air-fuel ratio changing from lean of stoichiometry to rich of stoichiometry when opening the throttle while cranking the engine without fuel.In any or all of the foregoing examples, additionally or alternatively, the indication of the absence of adsorbent material degradation is responsive to the exhaust air-fuel ratio remaining lean of stoichiometry when the engine is cranked without fuel while the throttle is open. In any or all of the foregoing examples, additionally or alternatively, the engine is coupled to a vehicle, and wherein cranking the engine without fuel includes cranking the engine via an electric motor while the vehicle is in a key-off condition. In any or all of the foregoing examples, additionally or alternatively, the exhaust air-fuel ratio is estimated via a heated exhaust gas oxygen sensor coupled to the exhaust system of the engine. In any or all of the foregoing examples, additionally or alternatively, the method further comprises, during an immediately subsequent engine operation, responsive to the indication of adsorbent material degradation, cranking the engine without fuel to direct fuel vapor from the engine intake to one or more catalysts coupled to the exhaust system at the completion of an immediately subsequent engine cycle. Another example engine method includes: during engine shut-down conditions, saturating an air intake system hydrocarbon (AIS HC) trap coupled to an intake manifold of the engine by directing fuel vapor from a fuel tank to the intake manifold; ceasing to direct the fuel vapor to the intake manifold and then actively purging the AIS HC trap; and indicating degradation of the AIS HC trap in response to an air-fuel ratio in an exhaust system of the engine being lean of stoichiometry during the active purging of the AIS HC trap. In any of the foregoing examples, additionally or alternatively, saturating the AIS HC trap includes: actuating a fuel tank isolation valve (FTIV) contained in a conduit coupling the fuel tank to a vapor canister of an evaporative emission control system to a closed position; operating a fuel pump coupled to the fuel tank until a fuel vapor pressure in the fuel tank increases to a threshold pressure; and then directing fuel vapor from the fuel tank to the AIS HC trap. In any or all of the foregoing examples, additionally or alternatively, directing fuel vapors from the fuel tank to the AIS HC trap includes opening the FTIV, opening a canister purge valve (CPV) contained in a passage coupling the vapor canister to the intake manifold, and closing a canister ventilation valve (CVV) contained in a passage coupling the vapor canister to atmosphere, and wherein ceasing to direct the fuel vapors to the intake manifold includes closing the CPV.In any or all of the foregoing examples, additionally or alternatively, the method further includes, after ceasing to direct the fuel vapor to the intake manifold, cranking the engine without fuel, actuating a throttle valve coupled to the intake manifold upstream of the AIS HC trap to a closed position, monitoring exhaust air-fuel ratio via an oxygen sensor coupled to the engine exhaust manifold of the exhaust system, and actively purging the AIS HC trap in response to the exhaust air-fuel ratio being leaner than stoichiometric. In any or all of the foregoing examples, additionally or alternatively, actively purging the AIS HC trap includes cranking the engine without fuel and actuating the throttle valve to a wide-open position to flow ambient air through the AIS HC trap to the engine exhaust manifold. In any or all of the foregoing examples, additionally or alternatively, the engine propels a vehicle, including an autonomous vehicle and / or a hybrid vehicle, and wherein the engine is cranked via an electric motor during a vehicle key-off condition.

[0091] In yet another example, a system includes: a vehicle, including an autonomous vehicle and / or a hybrid vehicle; an electric motor; an engine, including an intake passage and an exhaust passage; an intake throttle coupled to the intake passage; a fuel vapor canister selectively coupled to the engine intake passage via a canister purge valve (CPV); a fuel tank, which supplies fuel to the engine, the fuel tank selectively coupled to the fuel vapor canister via a fuel tank isolation valve (FTIV); a fuel pump housed in the fuel tank; an air intake system hydrocarbon (AIS HC) trap located in the engine intake passage; a heated exhaust gas oxygen (HEGO) sensor coupled to the exhaust passage; and a controller having computer-readable instructions stored on a non-transitory memory, the computer-readable instructions, when executed during an engine shut-off condition, cause the controller to: isolate the fuel tank by closing the FTIV and operate the fuel pump to generate fuel vapor, direct the generated fuel vapor to the AIS HC trap by opening the FTIV and the CPV, crank the engine without fuel via the electric motor and operate the fuel pump to generate fuel vapor during a shut-off condition. The throttle is opened to a wide-open position after the HC trap directs fuel vapors, and in response to the exhaust air-fuel ratio being leaner than stoichiometric, indicates degradation of the AIS HC trap. In any of the foregoing examples, additionally or alternatively, ceasing to direct fuel vapors to the AIS HC trap includes ceasing operation of the fuel pump and closing the CPV. In any or all of the foregoing examples, additionally or alternatively, the controller further includes instructions for: indicating that the AIS HC trap is not degraded in response to the exhaust air-fuel ratio being richer than stoichiometric during engine cranking with the throttle wide open.

[0092] Note that the exemplary control and estimation routines included herein can be used in conjunction 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 executed by a control system including a controller in conjunction with various sensors, actuators, and other engine hardware. The specific routines described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multi-tasking, multi-threaded processing strategies, etc. Therefore, the various actions, operations, and / or functions shown can be performed in the order shown, in parallel, or in some cases omitted. Likewise, the processing 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 can be repeatedly performed depending on the specific strategy used. In addition, the actions, operations, and / or functions can graphically represent code programmed into the non-transitory memory of a computer-readable storage medium in the engine control system, where the actions are performed by executing instructions in a system including various engine hardware components in conjunction with an electronic controller.

[0093] It should be understood that the configurations and procedures disclosed herein are exemplary in nature, and these specific embodiments should not be construed in a limiting sense, as many variations are possible. For example, the above technology can be applied to V-6, I-4, I-6, V-12, opposed 4-cylinder, 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.

[0094] The following claims particularly point out certain combinations and subcombinations regarded as novel and non-obvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. These 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 through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, are also deemed to be included within the subject matter of the present disclosure.

[0095] According to the present invention, a method includes testing for degradation of an adsorbent material during an unfueled cranking of an engine by directing fuel vapor to the adsorbent material in an air intake of the engine with a throttle valve coupled to the engine air intake in a closed position and indicating the presence or absence of adsorbent material degradation based on air-fuel ratio conditions in an exhaust system of the engine when the throttle valve is opened.

[0096] According to an embodiment, the adsorbent material located in the engine intake comprises an air intake system hydrocarbon (AIS HC) trap coupled to the engine intake downstream of the throttle valve, and wherein the adsorbent material comprises one or more of carbon, activated carbon, or zeolite.

[0097] According to an embodiment, the fuel vapor is directed to the adsorbent from an evaporative emission control system coupled to a fuel tank, and wherein the fuel vapor is generated by operating a fuel pump coupled to the fuel tank, the method further comprising isolating the fuel tank by actuating a fuel tank isolation valve (FTIV) contained in a conduit coupling the fuel tank to a vapor canister of the evaporative emission control system to a closed position before generating the fuel vapor.

[0098] According to an embodiment, the present invention is further characterized by rotating the engine without fuel until the exhaust gas air-fuel ratio is leaner than the stoichiometric air-fuel ratio before generating the fuel vapor.

[0099] According to an embodiment, the present invention is further characterized in that directing fuel vapor to the adsorbent material includes: estimating a vapor pressure in the fuel tank via a fuel tank pressure sensor coupled to the fuel tank, and in response to the vapor pressure increasing above a threshold pressure, closing the throttle, opening the FTIV, opening a canister purge valve (CPV) contained in a passage coupling the vapor canister to the engine intake, closing a canister vent valve (CVV) contained in a passage coupling the vapor canister to atmosphere, and directing fuel vapor from the fuel tank to the engine intake.

[0100] According to an embodiment, the present invention is further characterized by allowing the fuel vapor to reside in the engine intake for a threshold duration while directing the fuel vapor to the adsorbent material, and after the threshold duration, running the engine without fuel with the throttle closed until the exhaust air-fuel ratio is lean of stoichiometric, and then opening the throttle to a wide-open position.

[0101] According to an embodiment, the invention is further characterized in that the indication of the presence of degradation of the adsorbent material is responsive to the exhaust air-fuel ratio changing from lean of stoichiometry to rich of stoichiometry when the throttle valve is opened while the engine is running without fuel.

[0102] According to an embodiment, the invention is further characterized in that the indication of absence of degradation of the adsorbent material is responsive to the exhaust air-fuel ratio remaining lean of stoichiometry when the engine is cranked without fuel while opening the throttle.

[0103] According to an embodiment, the engine is coupled to a vehicle, and wherein cranking the engine without fuel comprises cranking the engine via an electric motor when the vehicle is in a key-off condition.

[0104] According to an embodiment, the exhaust gas air-fuel ratio is estimated via a heated exhaust gas oxygen sensor coupled to the exhaust system of the engine.

[0105] According to an embodiment, the invention is further characterized by, during immediately subsequent engine operation, in response to an indication of adsorbent material degradation, at the completion of an immediately subsequent engine cycle, cranking the engine without fuel to direct fuel vapor from the engine intake via the engine cylinders to one or more catalysts coupled to the exhaust system.

[0106] According to the present invention, an engine method includes: during an engine off condition, saturating an air intake system hydrocarbon (AIS HC) trap coupled to an intake manifold of the engine by selectively directing fuel vapor from a fuel tank to the intake manifold; ceasing the directing of the fuel vapor to the intake manifold and then actively purging the AIS HC trap; and indicating degradation of the AIS HC trap in response to an air-fuel ratio in an exhaust system of the engine being lean of stoichiometry during the active purging of the AIS HC trap.

[0107] According to an embodiment, saturating the AIS HC trap includes actuating a fuel tank isolation valve (FTIV) contained in a conduit coupling the fuel tank to a vapor canister of an evaporative emission control system to a closed position; operating a fuel pump coupled to the fuel tank until fuel vapor pressure in the fuel tank increases to a threshold pressure; and then directing fuel vapor from the fuel tank to the AIS HC trap.

[0108] According to an embodiment, the invention is further characterized in that directing fuel vapors from the fuel tank to the AIS HC trap includes opening the FTIV, opening a canister purge valve (CPV) contained in a passage coupling the vapor canister to the intake manifold, and closing a canister ventilation valve (CVV) contained in a passage coupling the vapor canister to atmosphere, and wherein ceasing to direct the fuel vapors to the intake manifold includes closing the CPV.

[0109] According to an embodiment, the present invention is further characterized by cranking the engine without fuel after ceasing the introduction of the fuel vapor to the intake manifold, actuating a throttle valve coupled to the intake manifold upstream of the AIS HC trap to a closed position, monitoring exhaust air-fuel ratio via an oxygen sensor coupled to an engine exhaust manifold of the exhaust system, and actively purging the AIS HC trap in response to the exhaust air-fuel ratio being lean of a stoichiometric air-fuel ratio.

[0110] According to an embodiment, the invention is further characterized in that actively flushing the AIS HC trap includes cranking the engine without fuel and actuating the throttle to a wide open position to flow ambient air through the AIS HC trap to the engine exhaust manifold.

[0111] According to an embodiment, the engine propels a vehicle including an autonomous vehicle and / or a hybrid vehicle, and wherein the engine is cranked via an electric motor during a vehicle key-off condition.

[0112] According to the present invention, a system is provided, the system having: a vehicle, including an autonomous vehicle and / or a hybrid vehicle; an electric machine; an engine, including an intake passage and an exhaust passage; an intake throttle valve coupled to the intake passage; a fuel vapor canister selectively coupled to the engine intake passage via a canister purge valve (CPV); a fuel tank, which supplies fuel to the engine, the fuel tank selectively coupled to the fuel vapor canister via a fuel tank isolation valve (FTIV); a fuel pump housed in the fuel tank; an air intake system hydrocarbon (AIS HC) trap located in the engine intake passage; a heated exhaust gas oxygen (HEGO) sensor coupled to the exhaust passage; and a controller having computer-readable instructions stored on a non-transitory memory, the computer-readable instructions, when executed during an engine shut-off condition, causing the controller to: isolate the fuel tank by closing the FTIV and operate the fuel pump to generate fuel vapor, and direct the generated fuel vapor to the AIS by opening the FTIV and the CPV. HC trap, cranking the engine without fuel via the electric machine and opening the throttle to a wide-open position after stopping directing fuel vapor to the AIS HC trap, and indicating degradation of the AIS HC trap in response to an exhaust air-fuel ratio being lean of a stoichiometric air-fuel ratio.

[0113] According to an embodiment, the present invention is further characterized in that ceasing to direct fuel vapor to the AIS HC trap includes ceasing operation of the fuel pump and closing the CPV.

[0114] According to an embodiment, the controller further includes instructions for indicating that the AIS HC trap is not degraded in response to the exhaust air-fuel ratio being rich of stoichiometry during cranking of the engine and wide open throttle.

Claims

1. An engine method comprising: Degradation of the adsorbent material is tested during an unfueled engine cranking by directing fuel vapor to the adsorbent material in an air intake of the engine with a throttle valve coupled to the engine air intake in a closed position, and indicating the presence or absence of adsorbent material degradation based on air-fuel ratio conditions in an exhaust system of the engine when the throttle valve is opened.

2. The engine method of claim 1 , wherein the adsorbent material located in the engine intake comprises an air intake system hydrocarbon (AIS HC) trap coupled to the engine intake downstream of the throttle, and wherein the adsorbent material comprises one or more of carbon, activated carbon, or zeolite.

3. The engine method of claim 1 , wherein the fuel vapor is directed to the adsorbent from an evaporative emission control system coupled to a fuel tank, and wherein the fuel vapor is generated by operating a fuel pump coupled to the fuel tank, the engine method further comprising isolating the fuel tank by actuating a fuel tank isolation valve (FTIV) contained in a conduit coupling the fuel tank to a vapor canister of the evaporative emission control system to a closed position before generating the fuel vapor.

4. The engine method of claim 3, further comprising: The engine is cranked without fuel until an exhaust air-fuel ratio is lean of stoichiometry before generating the fuel vapor, the exhaust air-fuel ratio estimated via a heated exhaust gas oxygen sensor coupled to the exhaust system of the engine.

5. The engine method of claim 3, wherein directing fuel vapor to the adsorbent material comprises: estimating vapor pressure in the fuel tank via a fuel tank pressure sensor coupled to the fuel tank, and in response to the vapor pressure increasing above a threshold pressure, closing the throttle, opening the fuel tank isolation valve (FTIV), opening a canister purge valve (CPV) contained in a passage coupling the vapor canister to the engine air intake, closing a canister vent valve (CVV) contained in a passage coupling the vapor canister to atmosphere, and directing fuel vapor from the fuel tank to the engine air intake.

6. The engine method of claim 1 , further comprising: While directing the fuel vapor to the adsorbent material, the fuel vapor is allowed to reside in the engine intake for a threshold duration, and after the threshold duration, the engine is run without fuel with the throttle closed until an exhaust air-fuel ratio is lean of stoichiometric, and then the throttle is opened to a wide-open position.

7. The engine method of claim 1 , wherein the indication that degradation of the adsorbent material exists is responsive to an exhaust air-fuel ratio changing from lean of stoichiometry to rich of stoichiometry when the throttle valve is opened while the engine is cranking without fuel.

8. The engine method of claim 1, wherein the indication of the absence of degradation of the adsorbent material is responsive to an exhaust air-fuel ratio remaining lean of stoichiometry when the throttle is opened while cranking the engine without fuel. 9 . The engine method of claim 1 , wherein the engine is coupled to a vehicle, and wherein cranking the engine without fuel comprises cranking the engine via an electric motor when the vehicle is in a key-off condition.

10. The engine method of claim 1 further comprising: During an immediately subsequent engine operation, in response to an indication of adsorbent material degradation, upon completion of an immediately subsequent engine cycle, the engine is cranked without fuel to direct fuel vapor from the engine intake via engine cylinders to one or more catalysts coupled to the exhaust system.

11. An engine system comprising: vehicles, including autonomous vehicles; Motor; an engine including an intake duct and an exhaust duct; an intake throttle valve coupled to the intake passage; a fuel vapor canister selectively coupled to the engine intake passage via a canister purge valve (CPV); a fuel tank that supplies fuel to the engine, the fuel tank selectively coupled to the fuel vapor canister via a fuel tank isolation valve (FTIV); a fuel pump housed in the fuel tank; an air intake system hydrocarbon (AIS HC) trap located in the engine intake tract; a heated exhaust gas oxygen (HEGO) sensor coupled to the exhaust passage; and A controller having computer readable instructions stored on a non-transitory memory that, when executed during an engine shut-off condition, cause the controller to: saturating the hydrocarbon (AIS HC) trap by selectively directing fuel vapor from the fuel tank to the intake manifold during engine off conditions; ceasing to direct the fuel vapor to the intake manifold and then actively flushing the hydrocarbon (AIS HC) trap; and Degradation of the hydrocarbon (AIS HC) trap is indicated in response to an exhaust air-fuel ratio in an exhaust system of the engine being lean of stoichiometry during active purging of the hydrocarbon (AIS HC) trap.

12. The engine system of claim 11 , wherein saturating the hydrocarbon (AIS HC) trap comprises: The fuel tank isolation valve (FTIV) is actuated to a closed position, the fuel pump is operated until the fuel vapor pressure in the fuel tank increases to a threshold pressure, and then fuel vapor is directed from the fuel tank to the hydrocarbon (AIS HC) trap.

13. The engine system of claim 12, wherein directing fuel vapors from the fuel tank to the hydrocarbon (AIS HC) trap comprises: opening the fuel tank isolation valve (FTIV), opening the canister purge valve (CPV), and closing a canister vent valve (CVV) contained in a passage coupling the fuel vapor canister to atmosphere, and wherein ceasing directing the fuel vapors to the intake manifold includes closing the canister purge valve (CPV).

14. The engine system of claim 11 , wherein the controller further comprises computer-readable instructions for: cranking the engine without fuel after ceasing the induction of the fuel vapor to the intake manifold, actuating the intake throttle to a closed position, monitoring the exhaust air-fuel ratio via the heated exhaust gas oxygen (HEGO) sensor, and actively purging the hydrocarbon (AIS HC) trap in response to the exhaust air-fuel ratio being lean of stoichiometric.

15. The engine system of claim 14, wherein actively flushing the hydrocarbon (AIS HC) trap comprises: The engine is cranked without fuel, and the intake throttle is actuated to a wide-open position to allow ambient air to flow through the hydrocarbon (AIS HC) trap to the engine exhaust.

16. An engine system comprising: vehicles, including hybrid vehicles; Motor; an engine including an intake duct and an exhaust duct; an intake throttle valve coupled to the intake passage; a fuel vapor canister selectively coupled to the engine intake passage via a canister purge valve (CPV); a fuel tank that supplies fuel to the engine, the fuel tank selectively coupled to the fuel vapor canister via a fuel tank isolation valve (FTIV); a fuel pump housed in the fuel tank; an air intake system hydrocarbon (AIS HC) trap located in the engine intake tract; a heated exhaust gas oxygen (HEGO) sensor coupled to the exhaust passage; and A controller having computer readable instructions stored on a non-transitory memory that, when executed during an engine shut-off condition, cause the controller to: saturating the hydrocarbon (AIS HC) trap by selectively directing fuel vapor from the fuel tank to the intake manifold during engine off conditions; ceasing to direct the fuel vapor to the intake manifold and then actively flushing the hydrocarbon (AIS HC) trap; and Degradation of the AIS HC trap is indicated in response to an exhaust air-fuel ratio in an exhaust system of the engine being lean of stoichiometry during active purging of the AIS HC trap.

17. The engine system of claim 16, wherein saturating the hydrocarbon (AIS HC) trap comprises: The fuel tank isolation valve (FTIV) is actuated to a closed position, the fuel pump is operated until the fuel vapor pressure in the fuel tank increases to a threshold pressure, and then fuel vapor is directed from the fuel tank to the hydrocarbon (AIS HC) trap.

18. The engine system of claim 17, wherein directing fuel vapors from the fuel tank to the hydrocarbon (AIS HC) trap comprises: opening the fuel tank isolation valve (FTIV), opening the canister purge valve (CPV), and closing a canister vent valve (CVV) contained in a passage coupling the fuel vapor canister to atmosphere, and wherein ceasing directing the fuel vapors to the intake manifold includes closing the canister purge valve (CPV).

19. The engine system of claim 16 , wherein the controller further comprises computer readable instructions for: cranking the engine without fuel after ceasing to direct the fuel vapor to the intake manifold, actuating the intake throttle to a closed position, monitoring the exhaust air-fuel ratio via the heated exhaust gas oxygen (HEGO) sensor, and actively purging the hydrocarbon (AIS HC) trap in response to the exhaust air-fuel ratio being lean of stoichiometric.

20. The engine system of claim 19, wherein actively flushing the hydrocarbon (AIS HC) trap comprises: The engine is cranked without fuel, and the intake throttle is actuated to a wide-open position to allow ambient air to flow through the hydrocarbon (AIS HC) trap to the engine exhaust.

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