System and method for diagnosing vehicle engine intake manifold and exhaust system

Abstract

Methods and systems are provided for pinpointing a degradation source in a vehicle engine system. In one example, the method includes operating a vehicle engine in a forward direction and a reverse direction without fuel in no particular order, and recording first and second intake air flow rates in an intake passage of the engine, respectively. The degradation source is indicated based on the first and second air flow rates. In this way, degradation of the vehicle engine system can be pinpointed with respect to location in the intake manifold, the exhaust system, or the engine.

Description

Technical Field

[0001] The present description generally relates to methods and systems for assessing the presence or absence of degradation in a vehicle engine, an engine intake manifold, or an engine exhaust system.

[0002] Background Art / Summary of the Invention

[0003] An internal combustion engine combusts a mixture of fuel and air to generate torque to propel the vehicle. Specifically, air is drawn into the engine via the engine intake tract based on the position of the throttle valve, where it is then mixed with fuel. The air-fuel mixture is combusted within one or more engine cylinders, driving one or more pistons within the cylinders, thereby rotating the engine crankshaft. The byproducts of combustion within the engine cylinders are directed to one or more catalysts via an exhaust manifold before exiting into the atmosphere.

[0004] Over time, both the engine intake and exhaust systems may degrade. Any degradation in the intake manifold, exhaust system, or engine may result in reduced fuel economy and, in some cases, an increase in undesirable emissions. The inventors herein have recognized these issues.

[0005] Engine operation can be adjusted based on several parameters, such as the air flow rate provided to the engine. The measurement of the air flow provided to the engine can be determined by, for example, a mass air flow (MAF) sensor. However, the presence of any degradation downstream of the MAF sensor in the intake manifold may result in unmetered air being provided to the engine. As a result, the air-fuel ratio can be switched to lean. However, there are many other root causes of engine lean operation, such as unwanted combustion, an exhaust oxygen sensor that is not functioning as required, valve timing problems, a MAF sensor that is not functioning as required, and so on. Therefore, it can be challenging to specifically diagnose the presence or absence of degradation originating from the intake system or intake manifold that is located downstream of the MAF sensor. Similarly, if the degradation in the exhaust system is downstream of, for example, the exhaust oxygen sensor, it may be difficult to pinpoint the degradation.

[0006] US Patent No. US20090187301 teaches a method of diagnosing the presence or absence of degradation in an intake manifold of an engine by comparing manifold absolute pressure (MAP) to atmospheric pressure. In one example, a significant amount of degradation is indicated in response to the MAP being substantially equal to atmospheric pressure.

[0007] However, the inventors have recognized potential issues with this approach. For example, this approach cannot diagnose the presence or absence of degradation in a vehicle's exhaust system. Therefore, the inventors herein have developed systems and methods that address these issues. In one example, a method is provided that includes: rotating an engine of a vehicle in a forward direction and a reverse direction without fuel to obtain a first intake air flow rate and a second intake air flow rate, respectively, in an intake tract of the engine; and indicating a source of degradation originating from one of the engine, an intake manifold of the engine, or an exhaust system of the engine based on both the first air flow rate and the second air flow rate.

[0008] In one example, before rotating the engine in the forward direction and the reverse direction without fuel to obtain the first intake flow rate and the second intake flow rate, a set of baseline comparison data is obtained, which includes rotating the engine in the forward direction and the reverse direction without fuel to obtain the first baseline intake flow rate and the second baseline intake flow rate; and wherein rotating the engine in the forward direction and the reverse direction without fuel is performed via a motor powered by a battery.

[0009] In this way, degradation originating from one of the engine, the engine's intake manifold, or the engine's exhaust system can be self-diagnosed based on a single test diagnostic routine. By pinpointing where degradation exists within the engine system, repairs can be simplified, customer satisfaction can be improved, and the release of undesirable emissions into the atmosphere can be reduced.

[0010] The above advantages and other advantages and features of the present specification will be readily apparent from the following detailed description when considered alone or in conjunction with the accompanying drawings.

[0011] It should be understood that the above Summary is provided to introduce a series of concepts in a simplified form, which are further described in the Detailed Description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims that follow the Detailed Description. Furthermore, the claimed subject matter is not limited to implementations that address any disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 An exemplary vehicle propulsion system is schematically illustrated.

[0013] Figure 2 An exemplary vehicle system having a fuel system and an evaporative emissions system is schematically illustrated.

[0014] Figures 3A to 3CA block diagram of a vehicle's intake and exhaust system for an engine is schematically shown, illustrating potential locations of degradation.

[0015] Figure 4 A block diagram of an exemplary autonomous driving system is schematically shown.

[0016] Figures 5A to 5B An exemplary H-bridge circuit that may be used to rotate a vehicle engine in either a forward or reverse direction is schematically shown.

[0017] Figure 6 A high level flow chart is shown for indicating the presence or absence of degradation originating from the intake manifold, exhaust system, or engine.

[0018] Figure 7 A high-level flow chart is shown, which details the above Figure 6 Steps used in a method for obtaining baseline comparison data and for performing engine system diagnostics.

[0019] Figure 8 Shown can be used to explain Figure 6 An exemplary lookup table of the results of the method.

[0020] Figure 9 Shown for Figure 6 and Figure 7 An exemplary timeline of a method for performing engine system diagnostics. DETAILED DESCRIPTION

[0021] The following description relates to systems and methods for pinpointing a source of degradation originating from a vehicle's intake manifold, exhaust system, or engine. Such systems and methods may include rotating the engine in a forward (or default) direction and then in a reverse direction without fuel injection, where rotating the engine without fuel is performed by a hybrid vehicle such as a Figure 1More specifically, in order to diagnose a source of degradation in an engine system (the engine system includes an engine intake manifold, an engine exhaust system, and an engine), the air flow in the intake system and the air flow in the exhaust system of the vehicle may be monitored under a set of predetermined conditions and compared to a set of baseline air flow in the intake system and a baseline air flow in the exhaust system measured under a substantially identical set of predetermined conditions. Measuring the air flow in the intake system may be performed by a mass air flow (MAF) sensor positioned in the intake system, wherein the air flow in the intake system may be measured under conditions in which the engine is rotating in a forward direction and a reverse direction. Measuring the air flow in the exhaust system may be performed via a gasoline particulate filter (GPF) differential pressure sensor under conditions in which the engine is rotating in a forward direction, wherein the GPF differential pressure sensor is positioned in the exhaust system downstream of the exhaust manifold, such as Figure 2 By comparing the air flow in the intake system and the air flow in the exhaust system with baseline measurements obtained under conditions where no degradation exists in the engine system, the source of degradation can be pinpointed, such as from the intake manifold, exhaust system, or engine. Figures 3A to 3C In some examples, a set of predetermined conditions for performing baseline air flow measurements on the intake and exhaust systems, and performing test air flow measurements on the intake and exhaust systems, may include an indication that the vehicle is unoccupied. Thus, in some examples, such measurements may be performed in an unoccupied autonomous vehicle, wherein Figure 4 An exemplary autonomous vehicle control system is depicted. To rotate the engine in both the forward and reverse directions without adding fuel, an H-bridge circuit such as Figures 5A to 5B The H-bridge circuit is depicted here. Figure 6 A method for pinpointing a source of degradation in the intake manifold, exhaust system, or engine is shown. As discussed, this method may include baseline measurements of air flow in the intake system (at forward and reverse engine rotation) and air flow in the exhaust system (at forward engine rotation), as well as similar measurements taken during testing. Thus, Figure 7 A method for obtaining such measurements is shown in Figure 6 To interpret the results of such a diagnostic test, a lookup table (such as that described above) may be used. Figure 8 The results are analyzed using the lookup table depicted at . Figure 9 An exemplary timeline for conducting such an engine system test diagnostic routine is shown at .

[0022] Figure 1An exemplary vehicle propulsion system 100 is shown. Vehicle propulsion system 100 includes a fuel-burning engine 110 and a motor 120. As a non-limiting example, engine 110 includes an internal combustion engine, and motor 120 includes an electric motor. Motor 120 can be configured to utilize or consume a different energy source than engine 110. For example, engine 110 can consume liquid fuel (e.g., gasoline) to produce an engine output, while motor 120 can consume electrical energy to produce a motor output. As such, a vehicle having propulsion system 100 can be referred to as a hybrid electric vehicle (HEV).

[0023] Vehicle propulsion system 100 can utilize a variety of different operating modes depending on the operating conditions encountered by the vehicle propulsion system. Some of these modes can enable maintaining engine 110 in a shut-down state (i.e., set to a deactivated state), wherein fuel combustion at the engine is stopped. For example, under selected operating conditions, motor 120 can propel the vehicle via drive wheels 130, as indicated by arrow 122, while engine 110 is deactivated.

[0024] During other operating conditions, engine 110 may be set to a deactivated state (as described above), while motor 120 may be operated to charge energy storage device 150. For example, motor 120 may receive wheel torque from drive wheels 130, as indicated by arrow 122, wherein the motor may convert the vehicle's kinetic energy into electrical energy for storage at energy storage device 150, as indicated by arrow 124. This operation may be referred to as regenerative braking of the vehicle. Thus, in some examples, motor 120 may provide a generator function. However, in other examples, generator 160 may instead receive wheel torque from drive wheels 130, wherein the motor may convert the wheel's kinetic energy into electrical energy for storage at energy storage device 150, as indicated by arrow 162.

[0025] During still other operating conditions, engine 110 can operate by combusting fuel received from fuel system 140, as indicated by arrow 142. For example, engine 110 can be operated to propel the vehicle via drive wheels 130, as indicated by arrow 112, while motor 120 is deactivated. During other operating conditions, both engine 110 and motor 120 can each be operated to propel the vehicle via drive wheels 130, as indicated by arrows 112 and 122, respectively. A configuration in which both an engine and a motor can selectively propel the vehicle can be referred to as a parallel vehicle propulsion system. It should be noted that in some examples, motor 120 can propel the vehicle via a first set of drive wheels, and engine 110 can propel the vehicle via a second set of drive wheels.

[0026] In other examples, vehicle propulsion system 100 can be configured as a series-type vehicle propulsion system, in which the engine does not directly propel the drive wheels. Instead, engine 110 can be operated to provide power to motor 120, which in turn can propel the vehicle via drive wheels 130, as indicated by arrow 122. For example, during selected operating conditions, engine 110 can drive generator 160, as indicated by arrow 116, which can in turn supply electrical energy to one or more of motor 120 (as indicated by arrow 114) or energy storage device 150 (as indicated by arrow 162). As another example, engine 110 can be operated to drive motor 120, which can in turn provide generator functionality to convert engine output into electrical energy, which can be stored at energy storage device 150 for subsequent use by the motor.

[0027] In still other examples, which will be discussed in detail below, in some examples, the motor 120 can be used to rotate or spin the engine in an unfueled configuration. More specifically, the motor 120 can rotate the engine unfueled using electricity from an onboard energy storage device 150, which may include, for example, a battery, a capacitor, an ultracapacitor, etc. In the event that the motor 120 is used to rotate the engine unfueled, fuel injection to the engine cylinders may be prevented and spark may not be provided to each engine cylinder. As will be discussed in further detail below, in some examples, the engine may be rotated or spinned in a forward or default direction unfueled, while in other examples, the engine may be rotated or spinned in a reverse direction unfueled. For example, an H-bridge circuit (see Figures 5A to 5B ) to rotate the engine in the forward or reverse direction.

[0028] Fuel system 140 may include one or more fuel storage tanks 144 for storing fuel on the vehicle. For example, fuel tank 144 may store one or more liquid fuels, including but not limited to gasoline, diesel, and alcohol fuel. In some examples, fuel may be stored on the vehicle as a mixture of two or more different fuels. For example, fuel tank 144 may be configured to store a mixture of gasoline and ethanol (e.g., E10, E85, etc.) or a mixture of gasoline and methanol (e.g., M10, M85, etc.), wherein these fuels or fuel mixtures may be delivered to engine 110, as indicated by arrow 142. Other suitable fuels or fuel mixtures may be supplied to engine 110, where they may be burned at the engine to produce engine output. Engine output may be used to propel the vehicle, as indicated by arrow 112, or may be recharged to energy storage device 150 via motor 120 or generator 160.

[0029] In some examples, energy storage device 150 may be configured to store electrical energy that may be supplied to other electrical loads resident on the vehicle (besides the motor), including cabin heating and air conditioning systems, engine starting systems, headlights, cabin audio and video systems, etc. As non-limiting examples, energy storage device 150 may include one or more batteries and / or capacitors.

[0030] Control system 190 may communicate with one or more of engine 110, motor 120, fuel system 140, energy storage device 150, and generator 160. Control system 190 may receive sensory feedback information from one or more of engine 110, motor 120, fuel system 140, energy storage device 150, and generator 160. Control system 190 may send command signals to one or more of engine 110, motor 120, fuel system 140, energy storage device 150, and generator 160 in response to this sensory feedback. Control system 190 may receive an indication of a driver-requested output of the vehicle propulsion system from vehicle driver 102. For example, control system 190 may receive sensory feedback from a pedal position sensor 194 in communication with pedal 192. Pedal 192 may illustratively be a brake pedal and / or an accelerator pedal. Additionally, in some examples, control system 190 can communicate with a remote engine start receiver 195 (or transceiver) that receives a wireless signal 106 from a key fob 104 having a remote start button 105. In other examples (not shown), a remote engine start can be initiated via a cell phone or smartphone-based system where the user's cell phone sends data to a server and the server communicates with the vehicle to start the engine.

[0031] 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 (HEV), in which electrical energy may be supplied from power source 180 to energy storage device 150 via power transmission cable 182. During operation to recharge energy storage device 150 from power source 180, power transmission cable 182 may electrically couple energy storage device 150 and power source 180. When the vehicle propulsion system is operating to propel the vehicle, power transmission cable 182 may be disconnected between power source 180 and energy storage device 150. Control system 190 may identify and / or control the amount of electrical energy stored at the energy storage device, which may be referred to as the state of charge (SOC).

[0032] In other examples, electrical transmission cable 182 may be omitted, where electrical energy may be wirelessly received from power source 180 at energy storage device 150. For example, energy storage device 150 may receive electrical energy from power source 180 via one or more of electromagnetic induction, radio waves, and electromagnetic resonance. Thus, it should be understood that any suitable means may be used to recharge energy storage device 150 from a power source that is not part of the vehicle. In this manner, motor 120 may propel the vehicle using an energy source other than the fuel used by engine 110.

[0033] Fuel system 140 may periodically receive fuel from a fuel source residing external to the vehicle. As a non-limiting example, vehicle propulsion system 100 may be refueled by receiving fuel via fuel dispensing device 170, as indicated by arrow 172. In some examples, fuel tank 144 may be configured to store fuel received from fuel dispensing device 170 until the fuel is supplied to engine 110 for combustion. In some examples, control system 190 may receive an indication of the level of fuel stored in fuel tank 144 via a fuel level sensor. The level of fuel stored at fuel tank 144 (e.g., as indicated by the fuel level sensor) may be communicated to the vehicle driver, for example, via a fuel gauge or an indication in vehicle instrument panel 196.

[0034] The vehicle propulsion system 100 may also include an ambient temperature / humidity sensor 198, and roll stability control sensors, such as one or more lateral and / or longitudinal and / or yaw rate sensors 199. The vehicle instrument panel 196 may include one or more indicator lights and / or a text-based display in which messages are displayed to the driver. The vehicle instrument panel 196 may also include various input portions for receiving driver input, such as buttons, a touch screen, voice input / recognition, etc. For example, the vehicle instrument panel 196 may include a refuel button 197 that can be manually actuated or pressed by the vehicle driver to initiate a refuel. For example, as described in more detail below, in response to the vehicle driver actuating the refuel button 197, the fuel tank in the vehicle may be depressurized, allowing for a refuel.

[0035] The control system 190 can be communicatively coupled to other vehicles or infrastructure using appropriate communication technologies. For example, the control system 190 can be coupled to other vehicles or infrastructure via a wireless network 131, which may include Wi-Fi, Bluetooth, a cellular service, a wireless data transmission protocol, or the like. The control system 190 can broadcast (and receive) information about vehicle data, vehicle diagnostics, traffic conditions, vehicle location information, vehicle operating procedures, and the like via vehicle-to-vehicle (V2V), vehicle-to-infrastructure-to-vehicle (V2I2V), and / or vehicle-to-infrastructure (V2I) technologies. Communications between vehicles and information exchanged between vehicles can be direct between vehicles or can be multi-hop. In some examples, longer-range communications (e.g., WiMax) can be used in conjunction with V2V or V2I2V to extend coverage by several miles. In still other examples, the vehicle control system 190 may be communicatively coupled to other vehicles or infrastructure via the wireless network 131 and the Internet (eg, the cloud), as is generally known in the art.

[0036] The vehicle system 100 may also include an onboard navigation system 132 (e.g., a global positioning system) with which the vehicle driver can interact. The navigation system 132 may include one or more position sensors to help estimate vehicle speed, vehicle altitude, vehicle heading / position, etc. This information can be used to infer engine operating parameters, such as local atmospheric pressure. As discussed above, the control system 190 may be further configured to receive information via the Internet or other communication networks. The information received from the GPS may be cross-referenced with information available via the Internet to determine local weather conditions, local vehicle regulations, etc. In one example, the information received from the GPS may be used in conjunction with a route learning method so that the vehicle control system 190 can learn the routes that the vehicle typically travels. In some examples, additionally or alternatively, other sensors (e.g., 133) such as lasers, radars, sonars, acoustic sensors, etc. may be used in conjunction with the onboard navigation system to perform route learning on the routes that the vehicle typically travels.

[0037] The vehicle system 100 may also include sensors dedicated to indicating the occupancy status of the vehicle, such as seat load sensors 107 , door sensing technology 108 , and onboard cameras 109 .

[0038] Figure 2 A schematic depiction of a vehicle system 206 is shown. It is understood that the vehicle system 206 may include Figure 1The vehicle system 206 is the same vehicle system as the vehicle system 100 depicted herein. The vehicle system 206 includes an engine system 208 coupled to an emission control system 251 and a fuel system 218. It will be appreciated that the fuel system 218 may include Figure 1 Emission control system 251 includes a fuel vapor container or canister 222 that can be used to capture and store fuel vapors. In some examples, vehicle system 206 can be a hybrid electric vehicle system.

[0039] Engine system 208 may include engine 110 having a plurality of cylinders 230. Although not explicitly shown, it is understood that each cylinder may include one or more intake valves and one or more exhaust valves. Engine 110 includes an engine intake passage 223 and an engine exhaust passage 225. Engine intake passage 223 includes a throttle valve 262, which is in fluid communication with engine intake manifold 244 via intake passage 242. Throttle valve 262 may include an electronic throttle valve that can be controlled by a vehicle controller that sends a signal to actuate the throttle valve to a desired position. In the example where the throttle valve is an electronic throttle valve, the power used to control the throttle valve to the desired position may be derived from an onboard energy storage device (e.g., 150), such as a battery. In addition, engine intake passage 223 may include an air box and a filter 215 positioned upstream of throttle valve 262. Engine exhaust system 225 includes an exhaust manifold 248 that opens into exhaust passage 235, which directs exhaust gas to the atmosphere. Engine exhaust system 225 may include one or more emission control devices or exhaust catalysts 270 that may be mounted in a close-coupled position within the exhaust system. The one or more emission control devices may include a three-way catalyst, a lean NOx trap, a diesel particulate filter, an oxidation catalyst, and the like. It should be understood that other components may be included in the engine, such as various valves and sensors. For example, an atmospheric pressure sensor 213 may be included in the engine intake. In one example, atmospheric pressure sensor 213 may be a manifold air pressure (MAP) sensor and may be coupled to the engine intake downstream of throttle 262. Atmospheric pressure sensor 213 may rely on a partially open throttle state or a fully or wide-open throttle state, such as when throttle 262 is opened by an amount greater than a threshold, to accurately determine atmospheric pressure. Alternatively, MAP may be inferred from alternative engine operating conditions, such as mass air flow (MAF) as measured by MAF sensor 210 coupled to the intake manifold.

[0040] Engine exhaust system 225 may also include a gasoline particulate filter (GPF) 217. GPF 217 may include a particulate filter, a hydrocarbon trap, a catalyzed wash coat, or a combination thereof. In some examples, during operation of engine 110, GPF 217 may be periodically regenerated by operating at least one cylinder of the engine within a specific air-fuel ratio to increase the temperature of GPF 217 so that retained hydrocarbons and soot particles can be oxidized.

[0041] In some examples, temperature sensor 226 may be positioned upstream of the inlet of GPF 217, and temperature sensor 229 may be positioned downstream of GPF 217. Temperature sensors 226 and 229 may be used to assess the temperature of GPF 217 for, for example, regeneration purposes. Furthermore, the pressure in the exhaust system may be assessed by pressure sensor 263. Pressure sensor 263 may be, for example, a differential pressure sensor positioned upstream and downstream of GPF 217. Pressure sensor 263 may be used to determine the pressure at the inlet of GPF 217 in order to assess the operating conditions for introducing air into the inlet of GPF 217 for regeneration. Furthermore, in some examples, soot sensor 268 may be positioned downstream of GPF 217 to assess the level of soot released from GPF 217. Soot sensor 268 may be used, among other functions, to diagnose the operation of GPF 217.

[0042] The fuel system 218 may include a fuel tank 220 coupled to a fuel pump system 221. It will be appreciated that the fuel tank 220 may include the same fuel pump system as described above. Figure 1 14. The fuel tank 220 is the same fuel tank as the fuel tank 144 depicted at FIG. 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 110. Although only a single injector 266 is shown, additional injectors may be provided for each cylinder. It should be understood that fuel system 218 may be a returnless fuel system, a return fuel system, or various other types of fuel systems. Fuel tank 220 may hold a variety of fuel mixtures, including fuels with a range of alcohol concentrations, such as various gasoline-ethanol blends, including E10, E85, gasoline, etc., 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.

[0043] Vapors generated in fuel system 218 may be routed to evaporative emission control system 251, which includes fuel vapor canister 222, via vapor recovery line 231 before being purged into engine intake 223. Vapor recovery line 231 may be coupled to fuel tank 220 via one or more conduits and may include one or more valves for isolating the fuel tank during certain conditions. For example, vapor recovery line 231 may be coupled to fuel tank 220 via one or more of conduits 271, 273, and 275, or a combination thereof.

[0044] Furthermore, in some examples, one or more fuel tank vent valves may be positioned in conduits 271, 273, or 275. Among other functions, the fuel tank vent valves may allow the fuel vapor canister of the emission control system to be maintained at a low pressure or vacuum without increasing the rate at which fuel evaporates from the tank (which would otherwise occur if the fuel tank pressure were reduced). For example, conduit 271 may include a grade vent valve (GVV) 287, conduit 273 may include a fill limit venting valve (FLVV) 285, and conduit 275 may include a grade vent valve (GVV) 283. Furthermore, in some examples, recycle line 231 may be coupled to fuel refueling system 219. In some examples, the fuel refueling system may include a fuel cap 205 for sealing the fuel refueling system from the atmosphere. Fuel refueling system 219 is coupled to fuel tank 220 via fuel refueling pipe or neck 211.

[0045] In addition, refueling system 219 may include a refueling lock 245. In some examples, refueling lock 245 may be a fuel cap locking mechanism. The fuel cap locking mechanism may be configured to automatically lock the fuel cap in a closed position so that the fuel cap cannot be opened. For example, fuel cap 205 may remain locked via refueling lock 245 while the pressure or vacuum in the fuel tank is greater than a threshold value. In response to a refueling request, such as a request initiated by the vehicle driver, the fuel tank may be depressurized and unlocked after the pressure or vacuum in the fuel tank drops below a threshold value. The fuel cap locking mechanism may be a latch or clutch that prevents the fuel cap from being removed when engaged. The latch or clutch may be electrically locked, such as by a solenoid, or may be mechanically locked, such as by a pressure diaphragm.

[0046] In some examples, refuel lock 245 may be a filler pipe valve located at the mouth of fuel filler pipe 211. In such examples, refuel lock 245 may not prevent removal of fuel cap 205. Instead, refuel lock 245 may prevent insertion of a refuel pump into fuel filler pipe 211. The filler pipe valve may be electrically locked, such as by a solenoid, or mechanically locked, such as by a pressure diaphragm.

[0047] In some examples, refuel lock 245 can be a refuel door lock, such as a latch or clutch, that locks a refuel door located in a body panel of the vehicle. The refuel door lock can be electrically locked, such as by a solenoid, or mechanically locked, such as by a pressure diaphragm.

[0048] In the example where an electric mechanism is used to lock refuel lock 245, refuel lock 245 may be unlocked by a command from controller 212 (e.g., when the fuel tank pressure drops below a pressure threshold). In the example where a mechanical mechanism is used to lock refuel lock 245, refuel lock 245 may be unlocked by a pressure gradient (e.g., when the fuel tank pressure drops to atmospheric pressure).

[0049] 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 286b configured to temporarily capture fuel vapors (including vaporized hydrocarbons) and "running losses" (i.e., fuel that evaporates during vehicle operation) during fuel tank refill operations. In one example, the adsorbent 286b used is activated carbon. Emission control system 251 may also include a canister vent path or vent line 227 that directs gas from canister 222 to the atmosphere when storing or capturing fuel vapors from fuel system 218.

[0050] The charcoal canister 222 may include a buffer zone 222a (or buffer area), each of which includes an adsorbent. As shown, the volume of the buffer zone 222a may be smaller than the volume of the charcoal canister 222 (e.g., be a portion thereof). The adsorbent 286a in the buffer zone 222a may be the same as or different from the adsorbent in the charcoal canister (e.g., both may include charcoal). The buffer zone 222a may be positioned within the charcoal canister 222 so that during canister loading, fuel tank vapors are first adsorbed within the buffer zone, and then when the buffer zone is saturated, additional fuel tank vapors are adsorbed in the charcoal canister. In contrast, during canister cleaning, fuel vapors are first desorbed from the charcoal canister (e.g., to a threshold amount) and then desorbed from the buffer zone. In other words, the loading and unloading of the buffer zone is not consistent with the loading and unloading of the charcoal canister. Therefore, the role of the charcoal canister buffer zone is to slow down any sudden increase in fuel vapor flowing from the fuel tank to the charcoal canister, thereby reducing the possibility of any sudden increase in fuel vapor entering the engine. One or more temperature sensors 232 may be coupled to the charcoal canister 222 and / or coupled within it. When the adsorbent in the canister adsorbs fuel vapor, heat (adsorption heat) is generated. Similarly, when the adsorbent in the canister desorbs fuel vapor, heat is consumed. In this way, the adsorption and desorption of fuel vapor by the canister can be monitored and estimated based on temperature changes within the canister.

[0051] Vent line 227 may also allow fresh air to be drawn into canister 222 when purging stored fuel vapors from fuel system 218 to engine intake 223 via purge line 228 and purge valve 261. For example, purge valve 261 may be normally closed but may be opened during certain conditions to provide vacuum from engine intake manifold 244 to the fuel vapor canister for purging. In some examples, vent line 227 may include an air filter 259 positioned upstream of canister 222.

[0052] In some examples, the flow of air and vapor between canister 222 and the atmosphere can be regulated by a canister vent valve 297 coupled within vent line 227. When included, canister vent valve 297 can be a normally open valve, allowing fuel tank isolation valve (FTIV) 252 to control communication between fuel tank 220 and the atmosphere. FTIV 252 can be positioned within conduit 278 between the fuel tank and fuel vapor canister 222. FTIV 252 can be a normally closed valve that, when open, allows fuel vapor to vent from fuel tank 220 to fuel vapor canister 222. The fuel vapor can then be vented to the atmosphere or purged into engine air intake 223 via canister purge valve 261. As will be discussed in detail below, in some examples, the FTIV may not be included, while in other examples, the FTIV may be included.

[0053] The fuel system 218 can be operated in a variety of modes by the controller 212 by selectively adjusting various valves and solenoids. It will be appreciated that the control system 214 may include the same Figure 1 For example, the fuel system may be operated in a fuel vapor storage mode (e.g., during a fuel tank refueling operation and when the engine is not combusting air and fuel), wherein controller 212 may open isolation valve 252 (when included) while closing canister purge valve (CPV) 261 to direct refueling vapors into canister 222 while preventing fuel vapors from being directed into the intake manifold.

[0054] As another example, the fuel system can be operated in a refueling mode (e.g., when a vehicle operator requests refueling of the fuel tank), wherein controller 212 can open isolation valve 252 (when included) while maintaining canister purge valve 261 closed to depressurize the fuel tank before allowing fuel to be added to the fuel tank. In this way, isolation valve 252 (when included) can remain open during the refueling operation to allow refueling vapors to be stored in the canister. After refueling is complete, the isolation valve can be closed.

[0055] As another example, the fuel system can be operated in a canister purge mode (e.g., after the emission control device light-off temperature has been reached and the engine is burning air and fuel), where controller 212 can open canister purge valve 261 while closing isolation valve 252 (if included). Here, vacuum generated by intake manifold 244 of the operating engine can be used to draw fresh air through ventilation passage 227 and through fuel vapor canister 222 to purge stored fuel vapor into intake manifold 244. In this mode, fuel vapor purged from the canister is combusted in the engine. Purge can continue until the amount of fuel vapor stored in the canister falls below a threshold.

[0056] Controller 212 may form part of a control system 214. In some examples, control system 214 may be associated with Figure 1 The control system 214 is shown as receiving information from a plurality of sensors 216 (various examples of which are described herein) and sending control signals to a plurality of actuators 281 (various examples of which are described herein). As an example, the sensors 216 may include: an exhaust gas sensor 237 located upstream of the emission control device 270; a temperature sensor 233; a pressure sensor 291; a pressure sensor 282; a canister temperature sensor 232; a MAF sensor 210; and a pressure sensor 263. Other sensors (such as pressure, temperature, air-fuel ratio, and composition sensors) may be coupled to various locations in the vehicle system 206. As another example, the actuators may include a throttle 262, a fuel tank isolation valve 252, a canister purge valve 261, and a canister vent valve 297. The controller may receive input data from the various sensors, process the input data, and trigger the actuators in response to the processed input data based on instructions or code programmed therein corresponding to one or more routines. Figures 6 and 7 An exemplary control routine is described.

[0057] In some examples, the controller may be placed in a reduced power mode or sleep mode in which the controller maintains only basic functionality and operates with lower battery consumption than in a corresponding awake mode. For example, the controller may be placed in sleep mode after a vehicle stop event in order to perform diagnostic routines for a certain duration after the vehicle stop event. The controller may have a wake-up input that allows the controller to return to the awake mode based on input received from one or more sensors. For example, the opening of a vehicle door may trigger a return to the awake mode, or a remote start event may trigger a return to the awake mode. In other examples, particularly with respect to Figures 6 and 7The depicted methods may require the controller to be awake in order to perform such methods. For example, the wake-up capability may enable the circuit to wake the controller to obtain baseline comparison data or perform engine system diagnostics, as discussed in further detail below.

[0058] Controller 212 may intermittently perform an undesirable evaporative emissions detection routine on fuel system 218 and / or evaporative emissions system 251 to confirm the absence of undesirable evaporative emissions in the fuel system and / or evaporative emissions system. Thus, the evaporative emissions detection routine (engine-off test) may be performed while the engine is off, using engine-off natural vacuum (EONV) generated by changes in fuel tank temperature and pressure after engine shutdown and / or supplemental vacuum from the vacuum pump. Alternatively, the evaporative emissions detection routine may be performed while the engine is operating by operating the vacuum pump and / or using engine intake manifold vacuum. In some configurations, a canister vent valve (CVV) 297 may be coupled to vent line 227. CVV 297 may be used to regulate the flow of air and vapors between canister 222 and the atmosphere. The CVV may also be used in diagnostic routines. When a CVV is included, the CVV can be opened during fuel vapor storage operations (e.g., during fuel tank refueling and when the engine is not running) so that air stripped of fuel vapor after passing through the canister can be pushed out to the atmosphere. Similarly, during cleaning operations (e.g., during canister regeneration and when the engine is running), the CVV can be opened to allow fresh air flow to strip fuel vapor stored in the canister. In some examples, CVV 297 can be a solenoid valve, wherein the opening or closing of the valve is performed via actuation of a canister ventilation solenoid. In particular, the canister ventilation valve can be an open valve that closes when the canister ventilation solenoid is actuated. In some examples, CVV 297 can be configured as a latchable solenoid valve. In other words, when the valve is in a closed configuration, it latches in the closed state without requiring additional current or voltage. For example, the valve can be closed with a 100ms pulse and then opened with another 100ms pulse at a later point in time. In this way, the battery power required to maintain the CVV closed is reduced.

[0059] In another example, an engine system diagnostic may be performed to determine whether the source of the degradation originates from the engine's intake manifold, the engine's exhaust system, or the engine itself. Figures 6 and 7The method described herein discusses such examples in detail. As discussed herein, degradation of the intake manifold may refer to punctures, cracks, degraded gaskets, loose connections, or air leaks in the intake manifold. Degradation of the exhaust system may similarly refer to punctures, cracks, degraded gaskets, loose connections, or exhaust leaks in the exhaust system. It will be appreciated that degradation of the exhaust system may refer to engine systems located upstream of a GPF (e.g., 217) or a differential pressure sensor (e.g., 263) and downstream of an engine (e.g., 110). Finally, degradation of the engine may refer to improperly sealed intake / exhaust valves, undesirable camshaft timing, compression issues, problems that may cause the engine to not pump as efficiently as expected or required, or any other engine-specific issues.

[0060] Now turn Figures 3A to 3C , which show examples of degradation sources originating from the intake manifold, exhaust system or engine, respectively. Figures 3A to 3C A simplified block diagram of the engine system including the MAF sensor 210, intake manifold 244, engine 110, exhaust system 225, GPF 217, and differential pressure sensor 263 is shown. Figures 3A to 3C Indicates that the above Figure 2 A simplified block diagram of the engine system is depicted at . Figures 3A to 3C In each of these, as will be explained in detail below, a degradation source is shown, designated 310a, 310b, and 310c.

[0061] Now turn Figure 3A , which shows an example in which the degradation source 310a originates from the intake manifold 244. In this example, the degradation source 310a cannot be observed directly via the MAF sensor 210 because the degradation source is located downstream of the MAF sensor 210. However, when the engine is in operation, unmetered air may be drawn into the engine via the degradation source. Therefore, it can be understood that additional air (in addition to the air drawn through the intake passage (such as 242)) may be drawn into the engine, and therefore, the pressure in the exhaust system may be greater than the expected pressure, as monitored by the differential pressure sensor 263. Therefore, as will be discussed below with respect to Figures 6 to 9As discussed in further detail, in such an example, if the air flow rate, as indicated by MAF sensor 210, is substantially equal to the expected air flow rate under a set of predetermined conditions, but the exhaust flow rate (e.g., pressure in the exhaust system), as indicated by differential pressure sensor 263, is greater than the expected exhaust flow rate under the same (or substantially equivalent) set of predetermined conditions, then diagnosing a degradation source 310a in intake manifold 244 may be possible. Such an example may involve operating the engine in the forward direction without fuel to obtain MAF sensor data and differential pressure sensor data. In other words, the exhaust flow rate, as indicated by differential pressure sensor 263, may be greater than the expected exhaust flow rate because unmetered air is drawn into the engine via degradation source 310a and through the exhaust system when the engine is operating in the forward direction without fuel.

[0062] In another example, additionally or alternatively, it may be possible to diagnose a degradation source in the intake manifold by first operating the engine in the forward or default direction without fuel and monitoring air flow in the intake system via the MAF sensor, then operating the engine in the reverse direction without fuel and again monitoring air flow in the intake system via the MAF sensor. In this example, if degradation source 310a is present in the intake manifold, the MAF sensor data recorded when operating the engine in the forward direction without fuel may be greater than the MAF sensor data recorded when operating the engine in the reverse direction without fuel because less airflow may reach the MAF sensor when the engine is operating in the reverse direction without fuel due to degradation source 310a. In other words, when operating the engine in the forward direction without fuel, MAF sensor 210 may not detect unmetered air that may be drawn into the engine via degradation source 310a. However, when the engine is rotated in reverse, airflow in the intake passage created by rotating the engine in reverse may at least partially exit through degradation source 310 a, thereby resulting in less than expected air flow (e.g., compared to a baseline measurement in the absence of degradation) as monitored via the MAF sensor.

[0063] Now turn Figure 3B , which shows an example in which degradation source 310b originates from exhaust system 225. In this example, the degradation source cannot be directly observed via MAF sensor 210 or differential pressure sensor 263 alone. However, when the engine is in operation, such as when rotating in the forward direction without fuel, exhaust flow may be pushed or forced into the atmosphere via degradation source 310b, resulting in an overall lower exhaust flow as monitored via differential pressure sensor 263. Therefore, as will be described below with respect to Figures 6 to 9As discussed in further detail, if the mass air flow as indicated via MAF sensor 210 is substantially equal to the expected mass air flow under a set of predetermined conditions, but wherein the exhaust flow (e.g., pressure in the exhaust system) as indicated by differential pressure sensor 263 is less than the expected exhaust flow under the same (or substantially identical) set of predetermined conditions, then it may be possible to diagnose a source of degradation in exhaust system 225.

[0064] Now turn Figure 3C , which shows an example in which the degradation source 310c originates from the engine 110. As mentioned above, the degradation source 310c originating from the engine 110 may include improperly sealed intake / exhaust valves, undesirable camshaft timing, compression issues, or any other engine-specific issues that may cause the engine to not pump as efficiently as expected or required. In such an example, the MAF sensor 210 may not be directly used to infer the degradation source originating from the engine, and similarly, the differential pressure sensor 263 may not be directly used to infer such a degradation source. However, an engine having a degradation source may not pump as efficiently as expected, and therefore, the amount of air drawn into the intake passage (e.g., 242) may be less than the expected amount of air under a predetermined set of conditions. Similarly, because less air is being drawn into the engine via the intake passage overall, then less exhaust flow may occur as a result. Therefore, as will be discussed below with respect to Figures 6 to 9 As discussed in further detail, if the intake mass air flow, as indicated by MAF sensor 210, is substantially equal to the exhaust flow, as indicated by differential pressure sensor 263, with the engine running in a forward direction without fuel, but wherein both the intake mass air flow and the exhaust flow are lower than expected under a set of predetermined conditions, then it may be possible to diagnose a source of degradation originating from the engine 110.

[0065] In another example, if the air flow in the intake tract as monitored by the MAF sensor when the engine is running in a forward direction without fuel is substantially equal to the air flow in the intake as monitored by the MAF sensor when the engine is running in a reverse direction without fuel, but wherein the air flow in response to the engine running in both the forward and reverse directions is lower than expected air flow (e.g., lower than baseline comparison data), then it may be possible to diagnose a source of degradation originating from the engine 110.

[0066] As mentioned above about Figures 3A to 3CThe set of predetermined conditions discussed may include: engine speed at a predetermined speed (e.g., a predetermined RPM), a throttle position (e.g., 262) at a predetermined angle or opening level, the engine being rotated or turned without fuel via electric power from an on-board energy storage device (e.g., 150), etc. In addition, as discussed above, the "expected" air flow in the intake manifold and exhaust system may include air flow that has been previously established during conditions in which no source of degradation is indicated, under conditions in which the engine is turned in both forward and reverse directions without fuel. In other words, as will be discussed in further detail below, the expected air flow in the intake manifold (under forward and reverse engine rotation) and the expected air flow in the exhaust system (under forward engine rotation) may include air flow that is consistent with the above discussion of Figures 3A to 3C A baseline air flow in the intake manifold and a baseline air flow in the exhaust system under a substantially identical set of predetermined conditions are discussed.

[0067] As discussed, systems and methods for diagnosing an engine system may include spinning or turning the engine without fuel to establish a baseline or expected air flow in the intake manifold and exhaust system under conditions where degradation has not yet been indicated. Furthermore, when performing engine system diagnostics that include comparing values ​​obtained via MAF sensor 210 and differential pressure sensor 263, the systems and methods may similarly include spinning or turning the engine without fuel. Thus, to avoid customer dissatisfaction caused by turning the engine without fuel, such engine system diagnostics may be performed while the vehicle driver and passengers are not indicated as being in the vehicle. Examples may include a remote start event while the vehicle is unoccupied, a "wake-up" of the vehicle controller after a key-off event for a predetermined duration while the vehicle is unoccupied, a "wake-up" of the vehicle controller immediately after a key-off event while the controller remains awake to perform diagnostics, and so forth. In yet another example, engine system diagnostics may be performed while the vehicle is indicated as unoccupied. In each of the above-mentioned examples, vehicle occupancy may be indicated by one or more of seat load sensors (eg, 107 ), door sensing technology (eg, 108 ), and / or one or more onboard cameras (eg, 109 ).

[0068] Because the engine system diagnostics discussed above may be performed in a vehicle configured as an autonomous vehicle, the following description of the engine system diagnostics discussed above may be performed in a vehicle configured as an autonomous vehicle. Figure 4 Discuss an exemplary autonomous driving system. Figure 4 It is possible to operate above Figure 11. A block diagram of an exemplary autonomous driving system 400 of the vehicle system 100 described above. The vehicle system 100 will be referred to herein as the "vehicle." As shown, the autonomous driving system 400 includes a user interface device 410, a navigation system 415, at least one autonomous driving sensor 420, and an autonomous mode controller 425. It will be understood that the vehicle navigation system 415 can be used in conjunction with the vehicle navigation system 415 described above. Figure 1 The in-vehicle navigation system 132 is the same as depicted there.

[0069] User interface device 410 may be configured to present information to vehicle occupants under conditions where vehicle occupants may be present. However, it will be appreciated that under certain conditions, the vehicle may operate autonomously without the presence of vehicle occupants. The information presented may include audible or visual information. Furthermore, user interface device 410 may be configured to receive user input. Thus, user interface device 410 may be located in a passenger compartment of the vehicle (not shown). In some possible implementations, user interface device 410 may include a touch-sensitive display screen.

[0070] The navigation system 415 may be configured to determine the vehicle's current location using, for example, a Global Positioning System (GPS) receiver configured to triangulate the vehicle's location relative to satellites or land-based transmitter towers. The navigation system 415 may be further configured to develop 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 410.

[0071] Autonomous driving sensors 420 may include any number of devices configured to generate signals to assist in navigating the vehicle. Examples of autonomous driving sensors 420 may include radar sensors, lidar sensors, vision sensors (e.g., cameras), vehicle-to-vehicle infrastructure networks, and the like. When vehicle 100 is operating in autonomous mode, autonomous driving sensors 420 may enable the vehicle to "see" the road and vehicle surroundings, and / or navigate around various obstacles. Autonomous driving sensors 420 may be configured to output sensor signals to, for example, autonomous mode controller 425.

[0072] The autonomous mode controller 425 can be configured to control one or more subsystems 430 while the vehicle is operating in autonomous mode. Examples of subsystems 430 controllable by the autonomous mode controller 425 include a braking subsystem, a suspension subsystem, a steering subsystem, and a powertrain subsystem. The autonomous mode controller 425 can control any one or more of these subsystems 430 by outputting signals to control units associated with the subsystems 430. In one example, the braking subsystem may include an anti-lock braking subsystem configured to apply braking force to one or more of the wheels (e.g., 130). Applying braking force to one or more of the wheels, as discussed herein, may be referred to as activating the brakes. To autonomously control the vehicle, the autonomous mode controller 425 can output appropriate commands to the subsystems 430. These commands can cause the subsystems to operate according to driving characteristics associated with the selected driving mode. For example, driving characteristics may include how aggressively the vehicle accelerates and decelerates, how much space the vehicle leaves behind the vehicle ahead, how frequently the autonomous vehicle changes lanes, and the like.

[0073] Figure 5A and Figure 5B An exemplary circuit 500 is shown that can be used to reverse the rotational orientation of an electric motor. Circuit 500 schematically depicts an H-bridge circuit that can be used to operate a motor 510 in a first (forward) direction and alternately in a second (reverse) direction. Circuit 500 includes a first (LO) side 520 and a second (HI) side 530. Side 520 includes transistors 521 and 522, while side 530 includes transistors 531 and 532. Circuit 500 also includes a power supply 540.

[0074] exist Figure 5A , transistors 521 and 532 are activated (energized), while transistors 522 and 531 are cut off. In this configuration, the left lead 551 of the motor 510 is connected to the power supply 540, and the right lead 552 of the motor 510 is connected to the ground. In this way, the motor 500 can run in the forward (or default) direction. When the engine is operated in the forward direction via the motor, the engine can be in a cranking mode for the start of initial combustion. Additionally and / or alternatively, when the engine is operated in the forward direction via the motor, the engine (and the motor or another motor) can be in a drive mode for driving the vehicle. It will be understood that in some examples, the engine can be rotated in the forward (e.g., default) direction under conditions where the vehicle is stationary, and it is only desirable to rotate or spin the engine in the forward direction without combustion.

[0075] exist Figure 5B, transistors 522 and 531 are active (energized), while transistors 521 and 532 are off. In this configuration, the right lead 552 of the motor 510 is connected to the power supply 540, and the left lead 551 of the motor 510 is connected to ground. In this way, the motor 510 can be operated in the reverse direction.

[0076] Now go to Figure 6 , illustrates a high-level exemplary method 600 for performing engine system diagnostics. More specifically, method 600 can be used to diagnose the presence or absence of degradation originating from a vehicle's intake manifold, exhaust system, or engine by comparing air flow in the intake system and air flow in the exhaust system under a set of predetermined conditions to baseline air flow in the intake system and baseline air flow in the exhaust system (under a substantially identical set of predetermined conditions). In this way, the source of degradation can be precisely pinpointed, whether in the intake manifold, exhaust system, or engine compartment. By pinpointing the source of degradation, repair procedures can be simplified, and operational issues related to the engine system can be quickly and accurately diagnosed, thereby increasing the service life of engine system components.

[0077] Reference will be made to the description and Figures 1 to 5B The method 600 is described with respect to the system shown in FIG. 1 , but it should be understood that similar methods may be applied to other systems without departing from the scope of the present disclosure. The method 600 may be performed by a controller such as Figure 2 The instructions for carrying out method 600 and the remaining methods included herein may be executed by the controller based on instructions stored on the controller's memory and in conjunction with signals received from sensors of the engine system, such as those described above with reference to FIG. Figures 1 to 4 The controller may employ engine system actuators, such as a motor (eg, 120 ), a throttle (eg, 262 ), a canister purge valve (eg, 261 ), etc., according to the following methods.

[0078] Method 600 begins at 605 and may include indicating whether conditions for obtaining baseline comparison data for engine system diagnostics are met, wherein the baseline comparison data includes measurements of air flow in the intake system under forward and reverse engine rotation conditions, and measurements of air flow in the exhaust system under forward (and, in some examples, reverse) engine rotation conditions. The conditions for obtaining the baseline comparison data being met may include an indication that the vehicle is unoccupied. As discussed above, seat load sensors, one or more onboard cameras, and / or door sensing technology may be utilized to ensure that the vehicle is unoccupied. Thus, the baseline comparison data may be obtained in response to a remote start event, or a controller awakening for a predetermined duration after a key-off event, or in the case of an autonomous vehicle that is unoccupied and not in motion. More specifically, if the vehicle is operating, for example, if the vehicle is being propelled by a motor (e.g., 120), an engine (e.g., 110), or some combination thereof, then the conditions for obtaining the baseline comparison data for engine system diagnostics may not be indicated as being met. Further, the condition indicated as being met at 605 may include an indication that no degradation source is present in the vehicle's intake manifold, exhaust system, or engine. For example, baseline comparison data may be initially obtained on a new engine system where it is believed that no degradation has occurred in any part of the engine system. Subsequently, in the absence of other indications (e.g., a sudden lean air / fuel ratio), baseline data may be periodically obtained via the controller on the non-degraded engine system. In the event of a sudden air / fuel ratio shift, the baseline comparison data to be used for engine system diagnostic testing (discussed below) may include the most recent baseline comparison data prior to the air / fuel ratio shift.

[0079] Additionally, the condition for obtaining baseline comparative data being satisfied at 605 may include an indication that baseline comparative data has not been obtained within a predetermined duration since the previous baseline comparative data measurement. In some examples, such a predetermined duration may include 1 day, more than 1 day but less than 2 days, more than 2 days but less than 5 days, more than 5 days but less than 10 days, more than 10 days, etc. If it is indicated at 605 that the condition for obtaining baseline comparative data is satisfied, then method 600 may proceed to 610, where the condition for obtaining baseline comparative data may be satisfied based on the predetermined duration. Figure 7 The method 700 depicted therein obtains baseline comparison data.

[0080] Alternatively, if the conditions for obtaining baseline comparison data at 605 are not indicated as being met, method 600 may proceed to 615 and may include indicating whether conditions for performing engine system diagnostics are met. The conditions for performing engine system diagnostics being met may similarly include an indication that the vehicle is unoccupied, which may include a remote start event, a controller awakened for a predetermined duration after a key-off event, or an autonomous vehicle being unoccupied. Furthermore, the conditions for performing engine system diagnostics at 615 being met may include an indication that baseline comparison data has been obtained within a threshold duration for the engine system diagnostics desired to be performed at 625. In some examples, the threshold duration since the baseline comparison data was obtained may include 1 day or less, more than 1 day but less than 2 days, more than 2 days but less than 3 days, etc. Further still, the conditions for performing engine system diagnostics at 615 being met may include an indication that the intake system filter (e.g., 215) has not been replaced since the baseline comparison data was obtained, and may also include an indication that the GPF (e.g., 217), if included, has not been regenerated since the baseline comparison data was obtained. Another example of a condition being met for performing an engine system diagnostic includes an indication that there has been no indication of a source of degradation in the intake manifold, exhaust system, or engine of the vehicle.

[0081] In yet another example, the conditions for performing an engine system diagnostic being met may include an indication of a disturbance in the air-fuel ratio, such as monitored via an exhaust gas sensor (e.g., 237). For example, if during a drive cycle in which the engine is operating (e.g., burning air and fuel), an indication is given that the engine system is operating lean (or rich), then one possibility is that there is a source of degradation originating from the intake manifold, the exhaust system, or the engine. For example, an indication that the engine is operating too lean may be provided based on a long-term combustion air-fuel ratio correction for lean air-fuel deviations. Therefore, if the engine system indicates an unexpected air-fuel ratio, such an indication may be stored at the controller. Storing such an indication at the controller may trigger an engine system diagnostic if all conditions for performing an engine system diagnostic at step 615 of method 600 are met.

[0082] If the conditions for performing engine system diagnostics are not met as indicated at step 615, method 600 may proceed to 620 and may include maintaining current vehicle operating parameters. For example, if the vehicle is not operating, with the engine off (not burning air and fuel) and the motor not being used to propel the vehicle, such conditions may be maintained. Alternatively, if the vehicle is operating, the current vehicle operating parameters may be maintained. In the exemplary case where an air-fuel ratio disturbance is indicated and therefore an engine system diagnostic is required, but where the conditions are not indicated as being met at 615, such an indication may be stored at the controller so that the engine system diagnostic can be triggered to be performed in response to the conditions for performing engine system diagnostics being met. In the case where one of the conditions not being met at 615 includes the absence of appropriate baseline comparison data (e.g., baseline comparison data obtained within a time period greater than a threshold duration prior to performing the engine system diagnostics, or obtained after the intake filter (e.g., 215) was replaced or the GPF (if applicable) was regenerated after the baseline comparison data was obtained), the method may include setting a flag at the controller and illuminating a malfunction indicator light on the vehicle instrument panel. Such an indication may alert the vehicle operator that the vehicle needs to be serviced for potential sources of degradation, such as from the intake manifold, exhaust system, or engine compartment, as engine system diagnostics may not be possible without appropriate baseline comparison data.

[0083] To prevent this situation, in some examples, the vehicle controller may prevent GPF regeneration in response to obtaining baseline comparison data until engine system diagnostics have been performed. However, the controller may rely on pressure measurements, as indicated by a differential pressure sensor (e.g., 263), to determine whether GPF regeneration is necessary at the expense of engine system diagnostics, or whether GPF regeneration may be prevented until engine system diagnostics have been performed. For example, if a threshold pressure differential (e.g., within 5%-10% or less of a pressure differential indicating GPF saturation) is obtained via a differential pressure sensor (e.g., 263) corresponding to the GPF during engine operation, it may be determined that the GPF may be regenerated, even though such an event may prevent engine system diagnostics from being performed until subsequent baseline comparison data is obtained.

[0084] In instances where the GPF is regenerated after the baseline comparative data is obtained so that new baseline comparative data can be obtained, a flag may be set at the controller indicating that the GPF was regenerated after the baseline comparative data was obtained so that new baseline comparative data can be obtained at the next available opportunity (e.g., when the conditions for obtaining the baseline comparative data are met, as discussed above).

[0085] A similar situation may arise if the intake filter is replaced after the baseline comparison data is obtained (e.g., 215). For example, in such a situation, a flag may be set at the controller that instructs the vehicle controller to subsequently obtain baseline comparison data at the next opportunity in which the conditions for obtaining baseline comparison data are indicated to be met.

[0086] Returning to step 615 of method 600, if the conditions for performing engine system diagnostics are indicated as being met, method 600 may proceed to 625 and may include: Figure 7 Performing Engine System Diagnostics It will be appreciated that both obtaining baseline comparison data and performing engine system diagnostics may include substantially identical methods encompassed by method 700 .

[0087] So now go to Figure 7 , shows a high-level exemplary method 700 for obtaining baseline comparison data and / or performing engine system diagnostics. More specifically, the method 700 can be used to obtain Figure 6 The depicted method 600 uses baseline comparison data to perform engine system diagnostics that rely on the baseline comparison data (and wherein performing engine system diagnostics also includes running method 700). In this way, the source of degradation can be pinpointed with respect to the vehicle's intake manifold, exhaust system, or engine. The baseline comparison data discussed herein may include measurements of air flow in the intake tract, as measured by a MAF sensor (e.g., 210), with the engine running in a forward direction without fuel and then in a reverse direction, and measurements of air flow in the exhaust system, as measured by a differential pressure sensor (e.g., 263), with the engine running in a forward direction without fuel and, in some examples, in a reverse direction. Similarly, "performing engine system diagnostics" may also include obtaining measurements of air flow in the intake tract, with the engine running in a forward direction without fuel and then in a reverse direction, and obtaining measurements of air flow in the exhaust system, with the engine running in a forward direction without fuel and, in some examples, in a reverse direction. It will be appreciated that measurements of both air flow in the intake tract and air flow in the exhaust system may be determined when the engine is turning in the forward direction, and vice versa.

[0088] Reference will be made to the description and Figures 1 to 5B The method 700 is described with reference to the system shown in FIG. 1 , but it should be understood that similar methods may be applied to other systems without departing from the scope of the present disclosure. The method 700 may be executed by a controller, such as Figure 2 The controller 212 in FIG. Figure 2As shown, the instructions may be stored as executable instructions in the controller as non-transitory memory. The instructions for performing method 700 and the remaining methods included herein may be executed by the controller based on the instructions stored on the controller's memory and in conjunction with signals received from sensors of the engine system, such as the sensors referenced above. Figures 1 to 4 According to the following method, the controller may use engine system actuators, such as the motor (eg, 120 ), the throttle (eg, 262 ), the canister purge valve (eg, 261 ), etc.

[0089] As discussed, method 700 may be performed to obtain a baseline, and then, method 700 comparison data may be utilized to perform engine system diagnostics, where the engine system diagnostics utilize the baseline comparison data to determine whether degradation originating from the vehicle's intake manifold, exhaust system, or engine is present. Therefore, method 700 will first be described with respect to obtaining baseline comparison data. Subsequently, a discussion will be provided regarding how method 700 may be used to perform engine system diagnostics.

[0090] Method 700 begins at 705 and may include controlling a throttle valve (e.g., 262) to a predetermined throttle position. As discussed above, such a throttle valve may include an electronic throttle valve that can be actuated to open or close via a vehicle controller using power supplied from an onboard energy storage device (e.g., 150), which may include, for example, a battery. The predetermined throttle position may include a position that is more open than a closed position, such as to allow intake air to be drawn into the engine via the intake manifold when the engine is rotating in a forward direction, and / or to allow air to be pushed to the atmosphere via the intake tract when the engine is rotating in a reverse direction (e.g., atmospheric air may be drawn into the engine via the exhaust system and pushed to the atmosphere via the engine's intake manifold and intake tract). For example, the throttle valve may be actuated to fully open, or to a fraction of fully open (e.g., 75%, 60%, 50%, 40%, 30%, 20%, etc.).

[0091] In response to controlling the throttle to a predetermined throttle position, method 700 may proceed to 710. At 710, method 700 may include rotating or turning the engine at a predetermined speed (e.g., a predetermined RPM) without fuel for a predetermined duration. The predetermined duration may include a duration for which a robust measurement of air flow may be obtained via a MAF sensor (e.g., 210) and via a differential pressure sensor (e.g., 263). Rotating the engine without fuel may include rotating the engine in the same direction as when the engine is operating to combust air and fuel. In other words, rotating the engine without fuel may include rotating the engine in a forward or default direction. Rotating the engine in a forward direction without fuel may include sequentially directing airflow through an intake tract of the engine, an intake manifold of the engine, the engine, and an exhaust system of the engine. Rotating the engine without fuel may also include rotating the engine via a motor (e.g., 120), wherein the motor may be powered via an onboard energy storage device (e.g., 150), such as a battery. The speed of the engine may be further controlled to a predetermined speed via the motor. The predetermined engine speed may include a speed at which a robust measurement of air flow can be obtained via a MAF sensor (e.g., 210) and via a differential pressure sensor (e.g., 263). Additionally, while not explicitly shown, it is understood that a canister purge valve (e.g., 261) may be maintained closed during engine cranking to ensure that air is not drawn from the evaporative emissions system and / or the fuel system. Still further, while not explicitly shown, for vehicles equipped with exhaust gas recirculation (EGR) (e.g., high pressure EGR and / or low pressure EGR), one or more valves controlling exhaust gas recirculation may be commanded or maintained closed. Still further, in order to crank the engine without fuel, the valve timing may be controlled to a default value.

[0092] With the engine running at a predetermined engine speed without fuel for a predetermined duration, method 700 may proceed to 715. At 715, method 700 may include obtaining measurements of air flow in the intake tract and air flow in the exhaust system. More specifically, a MAF sensor (e.g., 210) may be used at step 720 to obtain one or more first baseline intake air flow measurements, while a differential pressure sensor (e.g., 263) may be used at step 725 to obtain one or more first baseline exhaust air flow measurements. Such measurements may be obtained by taking one or more individual measurements over a predetermined duration while the engine is running without fuel. In instances where more than one measurement is obtained while the engine is running without fuel, the measurements may be averaged or otherwise processed to obtain a high confidence value for the desired measurement.

[0093] The measurements thus obtained may be stored at the vehicle controller for use in performing engine system diagnostics, as described below and in Figure 6 Further detailed discussion is provided in [1].

[0094] In response to obtaining the first baseline intake air flow measurement and the first baseline exhaust air flow measurement at steps 720 and 725, respectively, method 700 may proceed to 730. At 730, method 700 may include stopping the engine from rotating in the forward direction without fuel, and may also include maintaining the throttle in its current configuration. For example, a motor (e.g., 120) may be commanded to stop the engine, while a vehicle controller may send a signal to the electronic throttle to command or maintain the throttle in its current position.

[0095] In response to an indication that the engine has come to a standstill, method 700 may proceed to 735. At 735, method 700 may include rotating the engine in a reverse direction without fuel at a predetermined speed (e.g., a predetermined RPM) for a predetermined duration. Rotating the engine without fuel may include rotating the engine in a direction opposite to that in which the engine operates to combust air and fuel and in a direction opposite to the forward engine rotation depicted at step 710 of method 700. Rotating the engine in the reverse direction without fuel may include sequentially directing airflow through the exhaust system, the engine, the intake manifold, and the intake duct. In some examples, the predetermined duration and predetermined speed of engine rotation may be the same as indicated above at step 710 of method 700. However, in other examples, the predetermined duration and predetermined speed may be different when rotating or spinning the engine in the reverse direction compared to the forward direction. Similar to the discussion above for rotating the engine in the forward direction, rotating the engine in the reverse direction without fuel may include rotating the engine via a motor (e.g., 120), which may be powered via an onboard energy storage device (e.g., 150), such as a battery. To rotate the engine in the reverse direction, an H-bridge circuit may be utilized, such as in Figures 5A to 5BThe speed of the engine can be controlled to a predetermined speed via the motor. Similar to what is described above, the predetermined engine speed can include a speed at which a robust measurement of air flow can be obtained via a MAF sensor (e.g., 210) when the engine is rotating in the reverse direction. In addition, although not explicitly shown, it will be understood that the canister purge valve (e.g., 261) can be maintained closed during the engine rotation to ensure that air is not directed to the evaporative emissions system and / or the fuel system. Further, although not explicitly shown, for vehicles equipped with exhaust gas recirculation (EGR) (e.g., high pressure EGR and / or low pressure EGR), one or more valves controlling exhaust gas recirculation can be commanded or maintained closed. Still further, in order to rotate the engine in the reverse direction without fuel, the valve timing can be controlled to a default value.

[0096] With the engine running in the reverse direction without fuel at a predetermined engine speed, method 700 may proceed to 740. At 740, method 700 may include obtaining a measurement of air flow in the intake tract. More specifically, at step 740, a MAF sensor (e.g., 210) may be used to obtain one or more second baseline intake air flow measurements. Such measurements may be obtained by taking one or more separate measurements over a predetermined duration while the engine is running in the reverse direction without fuel. In instances where more than one measurement is obtained while the engine is running without fuel, the measurements may be averaged or otherwise processed to obtain a high confidence value for the desired measurement.

[0097] The measurements thus obtained can be stored at the vehicle controller for use in performing engine system diagnostics. Figure 6 Further detailed discussion is provided in [1].

[0098] In response to obtaining a second baseline intake air flow measurement while the engine is rotating in reverse, method 700 may proceed to 745. At 745, method 700 may include stopping the engine from rotating in reverse without fuel, and may also include returning the throttle to a default position or configuration. For example, the engine may be stopped by commanding a motor (e.g., 120) via a controller, while the vehicle controller may send a signal to the electronic throttle to actuate the throttle to a default position.

[0099] As mentioned above, it can be understood that Figure 7 The method discussed herein involves both obtaining baseline comparison data and performing engine system diagnostics after obtaining the baseline comparison data. As such, for the sake of brevity, the method will not be repeated. Therefore, it will be understood that the entire method 700 can be used with Figure 6 Used in conjunction to obtain baseline comparison data at step 610 and perform engine system diagnostics at step 625 .

[0100] More specifically, as discussed, method 700 can be used to first obtain baseline comparison data, and then subsequently used to perform engine system diagnostics. Therefore, if method 700 is used to obtain baseline comparison data, it will be understood that at step 720, method 700 may include obtaining a first baseline intake air flow rate, and at step 725, may include obtaining a first baseline exhaust air flow rate. Furthermore, at step 740, method 700 may include obtaining a second baseline intake air flow rate. Alternatively, if method 700 is used to perform engine system diagnostics, at step 720, method 700 may include obtaining a first intake air flow rate, and at step 725, may include obtaining a first exhaust air flow rate. Furthermore, at step 740, method 700 may include obtaining a second intake air flow rate. As discussed herein, obtaining the first intake air flow rate and the first exhaust air flow rate may include a first condition, and obtaining the second intake air flow rate may include a second condition. Furthermore, obtaining the first baseline intake air flow rate and obtaining the first baseline exhaust air flow rate may include a third condition, and obtaining the second baseline intake air flow rate may include a fourth condition. Thus, the first and third conditions involve rotating the engine in a forward direction, while the second and fourth conditions involve rotating the engine in a reverse direction.

[0101] Thus, returning to step 625 of method 600, in response to an indication that baseline comparison data has been obtained and conditions for performing engine system diagnostics are met, method 600 may include obtaining intake air flow measurements during both forward and reverse engine rotation, and obtaining exhaust air flow measurements during forward engine rotation and, in some examples, during reverse engine rotation, as described with respect to FIG. Figure 7 In response to obtaining such measurement results at 625, method 600 may proceed to 630. At step 630, method 600 may include: Figure 8 The results of the engine system diagnostics performed at step 625 are interpreted.

[0102] Therefore, go to Figure 8 , which shows an exemplary lookup table that can be used to interpret the results of engine system diagnostics. Such a lookup table can be stored, for example, at a vehicle controller. Figure 8 As shown there, there may be four different outcomes (AD) that may be generated through engine system diagnostics.

[0103] Result A may include a situation where, under conditions where the engine is running in the forward direction without fuel, the intake air flow measurement as measured by the MAF sensor is substantially equal to the baseline intake air flow measurement as measured by the MAF sensor, but the exhaust flow as monitored by the differential pressure sensor is greater than the baseline exhaust flow measurement as measured by the differential pressure sensor. In such an example, the presence of a degradation source originating from the intake manifold, such as described above, may be indicated. Figure 3A As discussed, a degradation source originating from the intake manifold may result in unmetered air being introduced into the engine, and therefore, the air flow in the exhaust system may be greater than would be expected under conditions where the degradation source is not present (e.g., under baseline conditions).

[0104] Additionally or alternatively, result A may include the following: if the intake flow measurement result measured by the MAF sensor while the engine is rotating in the forward direction without fuel is substantially equal to the baseline intake flow measurement result obtained during the engine rotation in the forward direction (see steps 710-725 of method 700), but if the intake flow measurement result measured by the MAF sensor while the engine is rotating in the reverse direction without fuel is less than the baseline intake flow measurement result obtained during the engine rotation in the reverse direction. In other words, this method of inferring whether there is degradation originating from the intake manifold may, in some examples, be performed in a vehicle that does not include a differential pressure sensor (e.g., 263). For example, because indicating the presence of a degradation source involves MAF sensor data under conditions in which the engine is rotating in the forward direction and then in the reverse direction, but may not involve differential pressure sensor data, this determination of intake manifold degradation may, in some examples, be performed in the absence of such differential pressure sensor data (which, in some examples, may include the absence of a differential pressure sensor in the exhaust system).

[0105] Result B may include the following situation: the intake air flow measurement as measured by the MAF sensor during the engine rotation in the forward direction without fuel is substantially equal to the baseline intake air flow measurement as measured by the MAF sensor during the engine rotation in the forward direction without fuel, but the exhaust flow as monitored by the differential pressure sensor is less than the baseline exhaust flow measurement as measured by the differential pressure sensor under the condition of the engine rotation in the forward direction without fuel. In this example, the presence of a degradation source originating from the exhaust system, such as the above-mentioned Figure 3BAs discussed, when the engine is running in the forward direction without fuel, a degradation source originating from the exhaust system may thus cause the exhaust flow to be forced into the atmosphere through the degradation source before reaching the differential pressure sensor. Consequently, this process may result in a differential pressure sensor reading that is lower than what would be expected under conditions where the degradation source is not present (e.g., under baseline conditions).

[0106] Additionally or alternatively, result B may include a situation where the intake airflow measurement as measured by the MAF sensor during engine rotation in the forward direction without fuel is substantially equal to the baseline measurement of airflow in the intake tract, but the intake airflow measurement as measured by the MAF sensor during engine rotation in the reverse direction without fuel is greater than the baseline measurement of airflow in the intake tract under similar conditions. In this example, it will be appreciated that, under conditions of engine rotation in the reverse direction without fuel, degradation in the exhaust system may cause additional air to be drawn into the engine via the degradation source in the exhaust system and forced through the engine to the intake tract.

[0107] Result C may include a scenario where the air flow in the intake tract, as measured by the MAF sensor, during engine rotation in the forward direction without fuel, and the air flow in the exhaust tract, as measured by the differential pressure sensor, during engine rotation in the forward direction without fuel, are both less than baseline measurements obtained using the MAF sensor and the differential pressure sensor during engine rotation in the forward direction without fuel. In this example, it can be appreciated that there may be a source of degradation related to engine operation originating from the engine compartment. As discussed, such sources of degradation may include: improperly sealing intake and / or exhaust valves; compression issues with one or more engine cylinders; degraded piston rings; degraded cylinder head gaskets; undesirable camshaft timing, etc. In such a scenario where the engine is identified as the source of degradation, the engine may not pump as expected, resulting in an overall decrease in air being drawn into the engine via the intake manifold and a correspondingly lower amount of exhaust gas flow being directed through the exhaust system.

[0108] Additionally or alternatively, result C may include a situation where the intake air flow rate measured by the MAF sensor under conditions where the engine is rotating in the forward direction without fuel is less than the baseline MAF sensor data obtained under conditions where the engine is rotating in the forward direction without fuel, and the intake air flow rate is less than the baseline intake air flow rate under conditions where the engine is rotating in the reverse direction without fuel. In this example, there may be degradation originating from the engine compartment because the air drawn into the intake system when the engine is rotating in the forward direction is generally less than the baseline measurement obtained under similar conditions of forward engine rotation, and because the air pushed through the intake system when the engine is rotating in the reverse direction is generally less than the baseline measurement obtained under similar conditions of reverse engine rotation. Therefore, it will be appreciated that this method of inferring whether there is degradation originating from the engine compartment can, in some examples, be performed in vehicles that do not include a differential pressure sensor (e.g., 263). For example, because the indication of whether a source of degradation exists involves MAF sensor data under conditions in which the engine is rotating in a forward direction and then in a reverse direction, but does not involve differential pressure sensor data, such a determination of engine compartment degradation may, in some examples, be made in the absence of such differential pressure sensor data (which, in some examples, may include the absence of a differential pressure sensor in the exhaust system).

[0109] Result D may include the following: the air flow in the intake tract, as measured by the MAF sensor, under conditions where the engine is running in the forward direction without fuel, and the air flow in the exhaust system, as measured by the differential pressure sensor, under conditions where the engine is running in the forward direction without fuel, are both substantially equal to baseline measurements taken by the MAF sensor and the differential pressure sensor under conditions where the engine is running in the forward direction without fuel. In this example, it may be indicated that there are no sources of degradation originating from the intake manifold, the exhaust system, and / or the engine.

[0110] Additionally or alternatively, result D may include the following: under conditions where the engine is running in the forward direction without fuel, the air flow in the intake tract, as measured by the MAF sensor, is substantially equal to the baseline air flow in the intake tract, and under conditions where the engine is running in the reverse direction without fuel, the air flow in the intake tract, as measured by the MAF sensor, is substantially equal to the baseline air flow in the intake tract. Therefore, it will be appreciated that this method of inferring the absence of degradation originating from the intake manifold, engine, or exhaust system may, in some examples, be performed in vehicles that do not include a differential pressure sensor (e.g., 263). For example, because the indication of the absence of a degradation source involves MAF sensor data under conditions where the engine is running in the forward direction and then in the reverse direction, but does not involve differential pressure sensor data, this determination of the absence of engine system degradation may, in some examples, be performed without such differential pressure sensor data (which, in some examples, may include the absence of a differential pressure sensor in the exhaust system).

[0111] It will be appreciated that, in each of the potential outcomes AD discussed above, sensor readings that are substantially equal to their respective baseline measurements may include measurements that are within a specific range of one another, such as measurements that differ by less than or equal to 5% across the span of the engine system diagnostic, or measurements that differ by less than or equal to 5% across the average of the span that includes the engine system diagnostic. Thus, it will be further appreciated that data that is less than / greater than the baseline data may include data that differs from the baseline data by more than 5%.

[0112] It will be further understood that there may be situations in which it may be desirable to perform engine system diagnostics or obtain baseline comparative data by rotating the engine in the forward direction without fuel, rather than in the reverse direction, or vice versa. For example, consider a situation in which the battery charge is low or limited, and therefore it may be undesirable to rotate the engine in both the forward and reverse directions to perform engine system diagnostics. Conversely, it may be desirable to rotate the engine only in the forward direction, for example, without fuel. In such an example, degradation of the intake tract, engine compartment, or exhaust system can be effectively diagnosed if the vehicle includes both a MAF sensor and a differential pressure sensor. However, in situations in which the vehicle does not include both a MAF sensor and a differential pressure sensor, the MAF sensor can be utilized to infer the presence or absence of degradation originating from the intake tract, engine compartment, or exhaust system under conditions of forward and reverse engine rotation (for obtaining baseline intake and exhaust flow rates, and for performing engine system diagnostics under similar conditions), as discussed above.

[0113] Return to Figure 6After interpreting the results of the engine system diagnostics at step 630 of method 600, method 600 may proceed to step 635. At step 635, method 600 may include adjusting vehicle operating parameters based on the results of the engine system diagnostics. For example, if a source of degradation is identified in the intake manifold, exhaust system, and / or engine, a malfunction indicator light on the vehicle's instrument panel may be illuminated, alerting the vehicle driver to request vehicle service.

[0114] If the source of degradation is indicated as originating from the intake manifold, then in some examples, the vehicle controller may adjust the throttle position during fueled engine operation to account for unmetered air entering the engine via the degradation source.

[0115] In other examples, where the source of degradation is indicated as originating from the intake manifold, exhaust system, or engine compartment, adjusting vehicle operating parameters may include the vehicle controller commanding an electric operating mode as frequently as possible to mitigate potential releases of undesirable emissions to the atmosphere and / or to mitigate potential mechanical issues with the engine if the engine ingests larger amounts of air than desired, or to mitigate existing issues in the engine compartment.

[0116] Thus, in one example, a method may include rotating an engine of a vehicle in a forward direction and a reverse direction without fuel to obtain a first intake air flow rate and a second intake air flow rate, respectively, in an intake tract of the engine. The method may also include indicating a source of degradation originating from one of the engine, an intake manifold of the engine, or an exhaust system of the engine based on both the first air flow rate and the second air flow rate.

[0117] In this method, before rotating the engine in a forward direction and a reverse direction without fuel to obtain a first intake air flow rate and a second intake air flow rate, the method may include obtaining a set of baseline comparison data, which includes rotating the engine in a forward direction and a reverse direction without fuel to obtain a first baseline intake air flow rate and a second baseline intake air flow rate. It will be appreciated that rotating the engine in a forward direction and a reverse direction without fuel may be performed via a motor powered by a battery.

[0118] In this method, obtaining the first baseline intake air flow rate and the second baseline intake air flow rate may include rotating the engine in a forward direction and a reverse direction under a set of conditions substantially equivalent to the conditions used to obtain the first intake air flow rate and the second intake air flow rate, respectively. For example, the substantially equivalent set of conditions may include rotating the engine in the forward direction at a first predetermined speed for a first predetermined duration; rotating the engine in the reverse direction at a second predetermined speed for a second predetermined duration; and controlling a throttle valve positioned in the intake manifold to a predetermined position during the rotation of the engine in the forward direction and the reverse direction.

[0119] In this method, obtaining the first intake air flow rate, the second intake air flow rate, the first baseline intake air flow rate, and the second baseline intake air flow rate may include: isolating the intake manifold and the engine from an evaporative emissions system of the vehicle; and isolating the engine, the intake manifold, and the exhaust system from an exhaust gas recirculation system, wherein the exhaust gas recirculation system is configured to recirculate at least a portion of exhaust gas from the engine to the intake manifold under predetermined engine operating conditions.

[0120] In this approach, it will be appreciated that obtaining the set of baseline comparison data includes conditions where the engine's intake manifold, the engine, and the engine's exhaust system are indicated as being free of sources of degradation.

[0121] In this method, in response to the first intake air flow being substantially equal to the first baseline intake air flow and the second intake air flow being substantially equal to the second baseline intake air flow, the engine, intake manifold, and exhaust system are indicated as free of degradation sources. Alternatively, in response to the first intake air flow being substantially equal to the first baseline intake air flow, but wherein the second intake air flow is less than the second baseline intake air flow, the degradation source may be indicated as the intake manifold. In another example, in response to the first intake air flow being less than the first baseline intake air flow and the second intake air flow being less than the second baseline intake air flow, the degradation source may be indicated as the engine. In yet another example, in response to the first intake air flow being substantially equal to the first baseline intake air flow, but wherein the second intake air flow is greater than the second baseline intake air flow, the degradation source may be indicated as the exhaust system.

[0122] Another example of a method includes: directing a first airflow sequentially through an intake duct of an engine, an intake manifold of the engine, the engine, and an exhaust system of the engine under a first condition; directing a second airflow sequentially through the exhaust system, the engine, the intake manifold, and the intake duct under a second condition; indicating a first intake flow rate under the first condition and indicating a second intake flow rate under the second condition; indicating a first exhaust flow rate under the first condition; and diagnosing the presence or absence of degradation originating from one of the intake manifold, the engine, or the exhaust system based on two or more of the first intake flow rate, the second intake flow rate, and / or the first exhaust flow rate.

[0123] In this method, the method may further include: under a third condition, indicating a first baseline intake air flow rate and indicating a first baseline exhaust air flow rate; and under a fourth condition, indicating a second baseline intake air flow rate. In this example, the third condition may include: sequentially directing a third airflow through an intake tract of the engine, an intake manifold of the engine, the engine, and an exhaust system of the engine, and the fourth condition may include: sequentially directing a fourth airflow through the exhaust system, the engine, the intake manifold, and the intake tract.

[0124] In this method, the first and third conditions may include rotating the engine in a forward direction via the motor without fuel to sequentially direct the first airflow through the intake duct, the intake manifold, the engine, and the exhaust system. In this method, the second and fourth conditions may include rotating the engine in a reverse direction via the motor without fuel to sequentially direct the second airflow through the exhaust system, the engine, the intake manifold, and the intake duct.

[0125] In this method, it can be understood that directing the first airflow includes directing the first airflow for a first predetermined duration, and directing the third airflow includes directing the third airflow for the first predetermined duration. As an example, directing the second airflow may include directing the second airflow for a second predetermined duration, and directing the fourth airflow may include directing the fourth airflow for a second predetermined duration, wherein the first predetermined duration is the same as or different from the second predetermined duration. In this method, each of the first, second, third, and fourth conditions may include controlling a throttle valve positioned in an intake tract of the vehicle to a predetermined open position. In this method, each of the first, second, third, and fourth conditions may include: isolating an evaporative emissions system from an intake tract, an intake manifold, an engine, and an exhaust system, the evaporative emissions system being configured to capture and store fuel vapor from the vehicle's fuel system; and each of the first, second, third, and fourth conditions includes: isolating the intake tract, the intake manifold, the engine, and the exhaust system from an exhaust gas recirculation system being configured to direct at least a portion of exhaust gas from the engine to the intake manifold.

[0126] In this method, the method may further include indicating the presence of degradation originating from the intake manifold in response to the first intake flow being substantially equal to the first baseline intake flow, and wherein the first exhaust flow is greater than the first baseline exhaust flow, and / or wherein the first intake flow is substantially equal to the first baseline intake flow and wherein the second intake flow is less than the second baseline intake flow. Alternatively, the method may include indicating the presence of degradation originating from the exhaust system in response to the first intake flow being substantially equal to the first baseline intake flow, and wherein the first exhaust flow is less than the first baseline exhaust flow, and / or wherein the first intake flow is substantially equal to the first baseline intake flow and wherein the second intake flow is greater than the second baseline intake flow. In yet another example, the method may include indicating the presence of degradation originating from the engine in response to the first intake flow being less than the first baseline intake flow and in response to the first exhaust flow being less than the first baseline exhaust flow, and / or wherein the first intake flow is less than the first baseline intake flow and wherein the second intake flow is less than the second baseline intake flow.

[0127] In this method, it will be appreciated that the third and fourth conditions can be performed under conditions where degradation in the intake manifold, engine, and exhaust system is not indicated. It will be further appreciated that the first, second, third, and fourth conditions can all be performed under conditions where the vehicle is unoccupied and not in motion. It will be further appreciated that the first intake air flow rate, the first baseline intake air flow rate, the second intake air flow rate, and the second baseline intake air flow rate can be indicated via a mass air flow sensor positioned in the intake manifold of the engine, and wherein the first exhaust air flow rate and the first baseline exhaust air flow rate are indicated via a differential pressure sensor positioned in the exhaust system.

[0128] Now turn Figure 9 , shown for use in accordance with and reference to Figures 6 to 8 As described and as used herein and with reference to Figures 1 to 5B The depicted system method for obtaining baseline comparison measurements and performing engine system diagnostics in a vehicle is shown in an exemplary timeline 900. Timeline 900 includes a curve 905 indicating whether the engine is off, or on and rotating in the forward (fwd) or reverse (rev) direction. Timeline 900 also includes a curve 910 indicating whether fuel injection to one or more engine cylinders is on or off over time. Timeline 900 also includes a curve 915 indicating whether the throttle (e.g., 262) is open, closed, or at some level between open and closed (e.g., a fraction of fully open). Timeline 900 also includes a curve 920 indicating engine speed (RPM) over time. The engine speed can be 0 (full stop) or can be greater than full stop (+). Timeline 900 also includes a curve 925 indicating the air flow in the vehicle intake tract as monitored by a MAF sensor (e.g., 210). The MAF sensor may indicate no air flow (0) or an air flow greater than no air flow (+). It will be appreciated that the air flow may be the air flow from the intake tract to the engine (when the engine is rotating in the forward direction) or the air flow from the engine and exhaust system to the intake tract (when the engine is rotating in the reverse direction).

[0129] Timeline 900 also includes a curve 930, which indicates the air flow in the exhaust system of the vehicle as monitored by a differential pressure sensor (e.g., 263). The differential pressure sensor may indicate no air flow (0), or may indicate an air flow greater than no air flow (+). It will be appreciated that the air flow in the exhaust system may include air flow from the engine to the exhaust system (with the engine rotating in the forward direction), or air flow from the exhaust system to the engine (with the engine rotating in the reverse direction). Timeline 900 also includes a curve 935, which indicates the air-fuel ratio as monitored over time via an exhaust gas sensor (e.g., 237). The air-fuel ratio may be stoichiometric (the ideal air-fuel ratio for burning all the fuel without excess air), or may be rich or lean of stoichiometry.

[0130] Timeline 900 also includes a curve 940 indicating whether conditions for obtaining baseline comparison data are indicated as being met, a curve 945 indicating whether conditions for performing engine system diagnostics are indicated as being met, a curve 950 indicating whether the vehicle is occupied, and a curve 955 indicating whether a degradation source exists in the engine system over time. The source can be the engine, the intake manifold (intake tract), or the exhaust system (exhaust tract).

[0131] At time t0, the engine is off (curve 905), and therefore, fuel is not injected into the engine cylinders (curve 910), and the engine speed is 0 RPM (curve 920). Although not explicitly shown, it is understood that at time t0, the vehicle is not propelled by the motor. The throttle position is substantially closed, reflecting the throttle position in the engine off / vehicle off state. With the engine off, there is no air-fuel ratio to measure, and therefore, no air-fuel ratio is indicated at time t0. Similarly, the MAF sensor located in the intake manifold downstream of the throttle does not record any air flow in the intake tract (curve 925), and the differential pressure sensor does not record any air flow in the exhaust system (curve 930). At time t0, the conditions for obtaining baseline comparison data are not indicated as being met (curve 940), and further, the conditions for performing engine system diagnostic tests are not indicated as being met (curve 945). There is no indication that the vehicle is occupied (plot 950 ), and no indication of degradation in the engine system (plot 955 ).

[0132] At time t1, the condition for obtaining baseline comparison data is indicated as being met (curve 940). The condition for obtaining baseline comparison data being met has been discussed with respect to step 605 of method 600 and will not be repeated here for the sake of brevity. However, it will be understood that in this exemplary timeline 900, the condition being met may include a situation where a predetermined duration has elapsed since the key-off event and where the controller is awakened to obtain baseline comparison data. In the event that the condition for obtaining baseline comparison data is met, the engine may be enabled to rotate in the forward (or default) direction. More specifically, the vehicle controller may command the motor (e.g., 120) to rotate the engine in the forward or default direction without fuel. Thus, fuel injection to the engine cylinders may be maintained off (curve 910). The motor may control the engine speed to a predetermined engine speed (curve 920). In addition, the throttle may be controlled to a predetermined throttle position (curve 915), as described above with respect to Figure 7 705 of the method 700 depicted herein.

[0133] The time period between time t1 and t2 may include a predetermined time period for rotating the engine in the forward direction without fuel. By rotating the engine in the forward direction without fuel, air can be drawn through the intake manifold and into the engine, and then directed to the exhaust system. Since fuel injection (and spark) is not provided to the engine cylinders, the air-fuel ratio indicates a lean burn condition (curve 935), as indicated by an exhaust gas sensor (e.g., 237). Between time t1 and t2, the air flow in the intake manifold is monitored by a MAF sensor (curve 925), and the air flow in the exhaust system is monitored via a differential pressure sensor (curve 930). As discussed, such measurements can be stored at the vehicle's controller so that subsequent measurements of the air flow in the intake manifold and subsequent measurements of the air flow in the exhaust system can be compared with the baseline measurements. In this way, potential sources of degradation originating from the intake manifold, exhaust system, or engine can be accurately pointed out.

[0134] After a predetermined period of time during which the engine rotates in the forward direction without fuel, the engine is controlled to 0 RPM via the electric motor. In other words, between times t2 and t3, the engine rotates to a standstill. However, the throttle valve is maintained in its current state to prevent throttle closure, and then is opened again to rotate the engine in the reverse direction.

[0135] Between times t2 and t3, with the engine cranked to a standstill, the air flow in the intake tract (curve 925) and the air flow in the exhaust system (curve 930) return to zero, or no flow. After the engine has cranked to a standstill, at time t3, the engine is controlled to rotate in the reverse direction without fuel. As discussed, an H-bridge circuit (such as Figures 5A to 5B the one depicted there) to enable the motor to rotate the engine in the reverse direction without adding fuel.

[0136] The time period between time t3 and t4 may include a predetermined time period for rotating the engine in the reverse direction without fuel. By rotating the engine in the reverse direction without fuel, air can be drawn through the exhaust system and into the engine, from which it is then directed to the engine intake. When air is drawn across the exhaust gas sensor, a lean burn condition is indicated (curve 935). Between time t3 and t4, the air flow in the intake tract is monitored by the MAF sensor (curve 925), and the air flow in the exhaust system is monitored via a differential pressure sensor (curve 930). As discussed, such measurements can be stored at the vehicle's controller so that subsequent measurements of the air flow in the intake tract and subsequent measurements of the air flow in the exhaust system can be compared with the baseline measurements. In this way, potential sources of degradation originating from the intake manifold, exhaust system, or engine can be accurately indicated, as discussed above and further discussed below.

[0137] After a predetermined rotational period of rotating the engine in the reverse direction without fuel, the engine is controlled to 0 RPM via the electric motor. In other words, between times t4 and t5, the engine is brought to a standstill. Furthermore, the throttle is actuated to a default configuration via the controller, which in this example comprises the configuration the throttle was in before the baseline comparison data was obtained. When the engine is brought to a standstill between times t4 and t5, air flow, as measured by the MAF sensor, decreases to zero flow in the intake tract, and air flow, as measured by the differential pressure sensor, decreases to zero flow in the exhaust system. Because baseline comparison data for both conditions of rotating the engine in the forward and reverse directions without fuel have already been obtained and stored at the controller, and the predetermined duration has elapsed at time t4, the condition for obtaining the baseline comparison data is no longer indicated as being met.

[0138] At time t5, the vehicle is occupied (curve 950). This indication may be provided via a door sensor, a seat load sensor, one or more onboard cameras, etc. Furthermore, the engine is on (curve 905), with fuel injection being provided to one or more engine cylinders (curve 910). In other words, at time t5, the vehicle operator has entered the vehicle and started the engine with the intent to drive the vehicle. With fuel injection being provided to the engine cylinders, it can be understood that the engine is operating in the forward direction, as indicated by curve 905.

[0139] Between time t5 and t6, the vehicle is driven, and therefore the throttle position (curve 915) varies according to the driver's demand, and the engine speed (curve 920) is controlled according to the driver's demand. With the engine in operation, the MAF sensor (curve 925) and the differential pressure sensor (curve 930) both measure the intake air flow and the exhaust air flow, respectively, which vary according to the driver's demand.

[0140] Between times t5 and t6, the air-fuel ratio remains substantially equal to the stoichiometric air-fuel ratio. However, at time t6, the air-fuel ratio switches to lean. As discussed above, changes in the air-fuel ratio can indicate potential degradation in the engine system. Therefore, it will be appreciated that, in response to the change in the air-fuel ratio indicated at time t6, such results can be stored at the vehicle controller so that engine system diagnostics can be initiated at the next opportunity when the conditions for performing engine system diagnostics are indicated to be met.

[0141] Between time t6 and t7, the vehicle continues to operate with the engine combusting air and fuel. In some examples, in response to the disturbance in the air-fuel ratio, adaptive fuel learning may correct the lean air-fuel ratio, as indicated by dashed line 936. However, in other examples, the vehicle may not include adaptive fuel learning.

[0142] At time t7, the engine is shut down (curve 905), and fueling of the engine is stopped (curve 910). In addition, at time t7, the vehicle becomes unoccupied again (curve 950).

[0143] After a period of time, at time t8, the conditions for performing engine system diagnostics are indicated as being met, as discussed above with respect to step 615 of method 600. For the sake of brevity, these conditions are not repeated here. However, it will be appreciated that in this exemplary timeline 900, the conditions being met may include a scenario in which a predetermined duration has elapsed since the key-off event, in which the controller is awakened to perform engine system diagnostics. Therefore, when the conditions for performing engine system diagnostics are met, the engine is enabled at time t8 to rotate in the forward or default direction. More specifically, the vehicle controller may command the motor (e.g., 120) to rotate the engine in the forward or default direction without fuel. Thus, fuel injection to the engine cylinders may be maintained off (curve 910). The motor may control the engine speed (curve 920) to the same engine speed as the engine speed during the period when the baseline comparison data was obtained (e.g., the engine speed between times t1 and t2). Additionally, the throttle may be controlled to the same predetermined throttle position as the throttle position during the period during which the baseline comparison data was obtained (eg, the throttle position between time t1 and t2 ).

[0144] The time period between time t8 and t9 may include a predetermined time period for rotating the engine in the forward direction without fuel to perform engine system diagnostics. More specifically, the predetermined time period for rotating the engine in the forward direction without fuel to perform engine system diagnostics may include the same predetermined time period (e.g., between time t1 and t2) for rotating the engine in the forward direction without fuel to obtain baseline comparison data. As discussed, by rotating the engine in the forward direction without fuel, air can be drawn through the intake tract and into the engine, and then directed to the exhaust system. Since fuel injection (and spark) is not provided to the engine cylinders, the air-fuel ratio indicates a lean burn condition (curve 935), as indicated by the exhaust gas sensor (e.g., 237). Between time t8 and t9, the air flow in the intake tract is monitored by the MAF sensor (curve 925), and the air flow in the exhaust system is monitored via the differential pressure sensor (curve 930). As discussed, such measurements can be stored at the vehicle's controller, allowing measurements of air flow in the intake and exhaust systems obtained during engine diagnostics by rotating the engine in a forward direction without fuel to be compared with baseline measurements obtained under the same conditions. In this way, potential sources of degradation originating in the intake manifold, exhaust system, or engine can be pinpointed.

[0145] After a predetermined period of time during which the engine rotates in the forward direction without fuel, the engine is controlled to 0 RPM via the electric motor. In other words, between times t9 and t10, the engine is brought to a standstill. However, the throttle valve is maintained in its current state to prevent throttle closure, and then reopened to rotate the engine in the reverse direction for engine system diagnostics.

[0146] Between times t9 and t10, with the engine cranked to a standstill, the air flow in the intake tract (curve 925) and the air flow in the exhaust system (curve 930) return to zero, or no flow. After the engine has cranked to a standstill, at time t10, the engine is controlled to rotate in the reverse direction without fuel. As discussed above, an H-bridge circuit (such as Figures 5A to 5B the one depicted there) to enable the motor to rotate the engine in the reverse direction without adding fuel.

[0147] The time period between times t10 and t11 may include a predetermined time period for rotating the engine in the reverse direction without fuel for performing engine system diagnostics. It will be appreciated that the predetermined time period for rotating the engine in the reverse direction without fuel for performing engine system diagnostics may include the same predetermined duration for rotating the engine in the reverse direction without fuel to obtain baseline comparison data. By rotating the engine in the reverse direction without fuel, air can be drawn through the exhaust system and into the engine, from which it is then directed to the engine intake. When air is drawn across the exhaust gas sensor, a lean burn condition is indicated (curve 935). Between times t11 and t12, air flow in the intake tract is monitored by the MAF sensor (curve 925), and air flow in the exhaust system is monitored via the differential pressure sensor (curve 930). As discussed, such measurements can be stored at the vehicle's controller for comparison with baseline measurements of air flow in the intake tract and exhaust system under similar conditions.

[0148] When the predetermined duration of rotating the engine in the reverse direction without fuel elapses, the conditions for performing engine system diagnostics are no longer indicated as being met (curve 945). Therefore, at time t11, the data related to the air flow in the intake duct acquired between times t8 and t9 is compared with the data acquired between times t1 and t2. In addition, the data acquired between times t10 and t11 is compared with the data acquired between times t3 and t4. As discussed above, a lookup table (such as Figure 8800 depicted at ) to diagnose the presence or absence of degradation in the engine system. More specifically, data acquired between times t1 and t2 includes baseline comparison data regarding air flow in the intake tract and exhaust system when the engine is running in the forward direction without fuel. This baseline comparison data may include: an averaged or otherwise processed first MAF baseline or first intake air flow baseline, represented by line 926, and an averaged or otherwise processed first differential pressure sensor baseline or first exhaust air flow baseline, represented by line 931. Similarly, data acquired between times t3 and t4 includes baseline comparison data regarding air flow in the intake tract and exhaust system when the engine is running in the reverse direction without fuel. This baseline comparison data may include an averaged or otherwise processed second MAF baseline or second intake air flow baseline, represented by line 927. Although not explicitly shown, in some examples, an averaged or otherwise processed second differential pressure sensor baseline or second exhaust air flow baseline may be generated by the controller.

[0149] As shown, the air flow in the intake tract (curve 925) obtained during the engine system diagnostics with the engine running in the forward direction without fuel (between times t8 and t9) is substantially equal to the first intake flow baseline represented by line 926. However, the air flow in the intake tract obtained during the engine system diagnostics with the engine running in the reverse direction without fuel (between times t10 and t11) is lower than the second intake flow baseline represented by line 927. Figure 8 , result A depicts a situation where the intake air flow when the engine is rotating in the forward direction is substantially equal to the baseline intake air flow, but the intake air flow when the engine is rotating in the reverse direction is less than the baseline. Therefore, at time t11, degradation of the intake manifold is indicated (curve 955). Data from the air flow in the exhaust system obtained during the period of rotating the engine in the forward direction supports this indication. Specifically, the air flow in the intake tract (curve 925) obtained during the engine system diagnosis with the engine rotating in the forward direction without fuel (between times t8 and t9) is substantially equal to the first intake air flow baseline represented by line 926. However, the air flow in the exhaust system (curve 930) obtained during the engine system diagnosis with the engine rotating in the forward direction without fuel (between times t8 and t9) is greater than the first exhaust flow baseline represented by line 931. Go to Figure 8 , Result A depicts the following situation: the intake air flow when the engine is running in the forward direction without fuel is substantially equal to the baseline intake air flow, but the air flow in the exhaust tract under the same conditions is greater than the baseline exhaust flow.

[0150] Thus, at time t11, degradation in the intake manifold is indicated (curve 955), and if the conditions for performing engine system diagnostics are no longer indicated as being met (curve 945), between times t11 and t12, the engine is deactivated (curve 905) and the motor cranks the engine to a standstill. Furthermore, the throttle position (curve 915) can be controlled or actuated to its default configuration via the controller. When the engine cranks to a standstill between times t11 and t12, the engine speed becomes 0 RPM (curve 920), air flow in the intake tract becomes zero flow (curve 925), and air flow in the exhaust system becomes zero flow (curve 930). After time t12, the engine remains off and the vehicle remains unoccupied. Although not explicitly shown, the vehicle controller can be placed in a sleep state in response to performing engine system diagnostics.

[0151] Although not explicitly discussed, it will be appreciated that in some examples, data related to exhaust flow obtained while the engine is running in reverse without fuel may be obtained to obtain a baseline exhaust flow when the engine is running in reverse without fuel, and may also be obtained to obtain exhaust flow when the engine is running in reverse without fuel for engine system diagnostics. For example, consider a scenario where the air flow in the exhaust system during the engine running in the forward direction without fuel is greater than the baseline air flow in the exhaust system obtained under the same conditions, and the air flow in the exhaust system during the engine running in the reverse direction without fuel is substantially equal to the baseline air flow in the exhaust system obtained under the same conditions. Such an indication may indicate degradation in the intake manifold. In another example, consider a scenario where the air flow in the exhaust system obtained while the engine is running in both the forward and reverse directions without fuel is lower than baseline data obtained under the same conditions. In such an example, such an indication may indicate degradation in the engine system compartment. In yet another example, consider a scenario where the air flow in the exhaust system achieved during engine rotation in a forward direction without fuel is less than a baseline air flow in the exhaust system achieved under similar circumstances, and the air flow in the exhaust system during engine rotation in a reverse direction without fuel is substantially equal to the baseline air flow in the exhaust system achieved under similar circumstances. In this example, such an indication may indicate degradation in the exhaust system.

[0152] In this way, degradation originating from one of the engine system's intake manifold, the exhaust system (located upstream of the differential pressure sensor and downstream of the engine), or the engine can be pinpointed by comparing intake and exhaust flow measurements with baseline intake and exhaust flow measurements obtained under conditions where the engine system is free of degradation. Pinpointing the source of degradation can improve customer satisfaction because the time spent by a technician working on the vehicle can be reduced. Furthermore, pinpointing the source of degradation can reduce the release of undesirable emissions into the atmosphere.

[0153] A technical effect is the recognition that degradation in the intake tract of a vehicle can be effectively diagnosed using a mass air flow sensor positioned in the intake tract of the engine by monitoring the air flow in the intake tract under conditions in which the engine is running in a forward direction and then in a reverse direction (or vice versa) without fuel, and comparing the air flow to a baseline air flow under similar conditions of forward and reverse engine rotation. Another technical effect is the recognition that degradation of the exhaust system and / or engine compartment can be similarly indicated by monitoring the air flow in the intake tract under conditions in which the engine is running in a forward direction and in a reverse direction without fuel.

[0154] Another technical effect is the recognition that, in some examples, engine system diagnostics can be performed by rotating the engine only in the forward direction, monitoring air flow in the intake tract and air flow in the exhaust system, and comparing the air flow rates to baseline air flow rates in the intake tract and exhaust system under similar conditions. For example, it is recognized that a mass air flow sensor located in the intake manifold of an engine may not be able to effectively diagnose a degradation source originating in the intake manifold by rotating the engine in the forward direction unless such mass air flow measurements are considered in conjunction with a pressure sensor or other sensor used to monitor air flow in the exhaust system. Similarly, under conditions where the engine is rotating in the forward direction (but not in the reverse direction), it may not be possible to directly infer a degradation source originating in the engine or exhaust system unless the intake and exhaust flow measurements are considered together. Thus, a technical effect is the recognition that, in some examples, engine system diagnostics can be performed by rotating the engine in the forward direction without fuel, but not in the reverse direction, which may be desirable in situations where battery power is low or limited. In all examples (e.g., degradation sources originating from the intake manifold, exhaust system, or engine), another technical effect is the recognition that intake and exhaust flow measurements can be compared to baseline intake and exhaust flow measurements obtained under similar conditions, such that the determination of the degradation source can be indicated by comparing both intake and exhaust flow measurements to the baseline intake and exhaust flow measurements, respectively. In this way, degradation sources originating from the intake manifold, exhaust system, or engine can be conclusively diagnosed.

[0155] In this article and reference Figures 1 to 5B The system described herein and with reference to FIG. Figures 6 and 7The described method can implement one or more systems and one or more methods. In one example, a method includes: rotating an engine of a vehicle in a forward direction and a reverse direction without fuel to obtain a first intake air flow rate and a second intake air flow rate in an intake tract of the engine, respectively; and indicating a source of degradation originating from one of the engine, an intake manifold of the engine, or an exhaust system of the engine based on both the first air flow rate and the second air flow rate. In a first example of the method, the method further includes: obtaining a set of baseline comparison data before rotating the engine in the forward direction and the reverse direction without fuel to obtain the first intake air flow rate and the second intake air flow rate, which includes rotating the engine in the forward direction and the reverse direction without fuel to obtain a first baseline intake air flow rate and a second baseline intake air flow rate; and wherein rotating the engine in the forward direction and the reverse direction without fuel is performed via a motor powered by a battery. A second example of the method optionally includes the first example and further includes: wherein obtaining the first baseline intake flow rate and the second baseline intake flow rate includes: rotating the engine in the forward direction and the reverse direction under a set of conditions that are substantially equivalent to the conditions used to obtain the first intake flow rate and the second intake flow rate, respectively, wherein the substantially equivalent set of conditions includes: rotating the engine in the forward direction at a first predetermined speed and for a first predetermined duration, rotating the engine in the reverse direction at a second predetermined speed and for a second predetermined duration, and controlling a throttle valve positioned in the intake manifold to a predetermined position during rotation of the engine in the forward direction and the reverse direction. A third example of the method optionally includes any one or more or each of the first and second examples, and further includes: wherein rotating the engine in the forward and reverse directions without fuel to obtain the first intake air flow rate, the second intake air flow rate, the first baseline intake air flow rate, and the second baseline intake air flow rate further includes: isolating the intake manifold and the engine from an evaporative emissions system of the vehicle; and isolating the engine, the intake manifold, and the exhaust system from an exhaust gas recirculation system, the exhaust gas recirculation system being configured to recirculate at least a portion of exhaust gas from the engine to the intake manifold under predetermined engine operating conditions. A fourth example of the method optionally includes any one or more or each of the first to third examples, and further includes: wherein obtaining the set of baseline comparison data is performed under conditions where the intake manifold of the engine, the engine, and the exhaust system of the engine are indicated as being free of the degradation source.A fifth example of the method optionally includes any one or more or each of the first through fourth examples, and further includes: wherein in response to the first intake air flow being substantially equal to the first baseline intake air flow and the second intake air flow being substantially equal to the second baseline intake air flow, the engine, the intake manifold, and the exhaust system are indicated as being free of the degradation source. A sixth example of the method optionally includes any one or more or each of the first through fifth examples, and further includes: wherein in response to the first intake air flow being substantially equal to the first baseline intake air flow, but wherein the second intake air flow is less than the second baseline intake air flow, the degradation source is indicated as being the intake manifold. A seventh example of the method optionally includes any one or more or each of the first through sixth examples, and further includes: wherein in response to the first intake air flow being less than the first baseline intake air flow and the second intake air flow being less than the second baseline intake air flow, the degradation source is indicated as being the engine. An eighth example of the method optionally includes any one or more or each of the first to seventh examples, and further includes: wherein in response to the first intake flow being substantially equal to the first baseline intake flow, but wherein the second intake flow is greater than the second baseline intake flow, the degradation source is indicated as being the exhaust system.

[0156] Another example of a method includes: directing a first airflow sequentially through an intake duct of an engine, an intake manifold of the engine, the engine, and an exhaust system of the engine under a first condition; directing a second airflow sequentially through the exhaust system, the engine, the intake manifold, and the intake duct under a second condition; indicating a first intake flow rate under the first condition and indicating a second intake flow rate under the second condition; indicating a first exhaust flow rate under the first condition; and diagnosing the presence or absence of degradation originating from one of the intake manifold, the engine, or the exhaust system based on two or more of the first intake flow rate, the second intake flow rate, and / or the first exhaust flow rate. In a first example of the method, the method further comprises: under a third condition, indicating a first baseline intake air flow rate and indicating a first baseline exhaust air flow rate; under a fourth condition, indicating a second baseline intake air flow rate; and wherein the third condition comprises directing a third airflow sequentially through an intake tract of the engine, the intake manifold of the engine, the engine, and the exhaust system of the engine; and wherein the fourth condition comprises directing a fourth airflow sequentially through the exhaust system, the engine, the intake manifold, and the intake tract. A second example of the method optionally includes the first example and further comprises: wherein the first and third conditions comprise rotating the engine in a forward direction via a motor without fuel to sequentially direct the first airflow through the intake tract, the intake manifold, the engine, and the exhaust system, and wherein the second and fourth conditions comprise rotating the engine in a reverse direction via the motor without fuel to sequentially direct the second airflow through the exhaust system, the engine, the intake manifold, and the intake tract.A third example of the method optionally includes any one or more or each of the first example and the second example, and further includes: wherein directing the first airflow includes directing the first airflow for a first predetermined duration, and wherein directing the third airflow includes directing the third airflow for the first predetermined duration; wherein directing the second airflow includes directing the second airflow for a second predetermined duration, wherein directing the fourth airflow includes directing the fourth airflow for the second predetermined duration, wherein the first predetermined duration is the same as or different from the second predetermined duration; wherein each of the first condition, the second condition, the third condition, and the fourth condition includes directing the first airflow to be positioned at the A throttle valve in the intake passage of the vehicle is controlled to a predetermined open position; and wherein each of the first, second, third, and fourth conditions includes isolating an evaporative emissions system from the intake passage, the intake manifold, the engine, and the exhaust system, the evaporative emissions system being configured to capture and store fuel vapor from a fuel system of the vehicle, and wherein each of the first, second, third, and fourth conditions includes isolating the intake passage, the intake manifold, the engine, and the exhaust system from an exhaust gas recirculation system, the exhaust gas recirculation system being configured to recirculate at least a portion of exhaust gas from the engine to the intake manifold. A fourth example of the method optionally includes any one or more or each of the first to third examples, and further includes: indicating the presence of degradation originating from the intake manifold in response to the first intake air flow being substantially equal to the first baseline intake air flow, and wherein the first exhaust air flow is greater than the first baseline exhaust air flow, and / or wherein the first intake air flow is substantially equal to the first baseline intake air flow and wherein the second intake air flow is less than the second baseline intake air flow. A fifth example of the method optionally includes any one or more or each of the first to fourth examples, and further includes: indicating the presence of degradation originating from the exhaust system in response to the first intake flow being substantially equal to the first baseline intake flow, and wherein the first exhaust flow is less than the first baseline exhaust flow, and / or wherein the first intake flow is substantially equal to the first baseline intake flow and wherein the second intake flow is greater than the second baseline intake flow. A sixth example of the method optionally includes any one or more or each of the first to fifth examples, and further includes: indicating the presence of degradation originating from the engine in response to the first intake flow being less than the first baseline intake flow and in response to the first exhaust flow being less than the first baseline exhaust flow, and / or wherein the first intake flow is less than the first baseline intake flow and wherein the second intake flow is less than the second baseline intake flow.A seventh example of the method optionally includes any one or more or each of the first to sixth examples, and further includes: wherein the third condition and the fourth condition are performed under conditions in which degradation in the intake manifold, the engine, and the exhaust system has not yet been indicated; wherein the first condition, the second condition, the third condition, and the fourth condition are all performed under conditions in which the vehicle is unoccupied and in which the vehicle is not in motion; and wherein the first intake flow, the first baseline intake flow, the second intake flow, and the second baseline intake flow are indicated via a mass air flow sensor positioned in the intake manifold of the engine, and wherein the first exhaust flow and the first baseline exhaust flow are indicated via a differential pressure sensor positioned in the exhaust system.

[0157] 14. The system of claim 13, further comprising: an engine system comprising an intake manifold, an exhaust system, and an engine; a mass air flow sensor positioned in the intake manifold; a motor capable of rotating the engine without fuel; and a controller storing instructions in a non-transitory memory that, when executed, cause the controller to: obtain a first baseline intake air flow via the mass air flow sensor by rotating the engine in a forward direction without fuel via the motor, and obtain a second baseline intake air flow via the mass air flow sensor by rotating the engine in a reverse direction without fuel via the motor just after rotating the engine in the forward direction without fuel to obtain the first baseline intake air flow; and in response to a command for performing an engine system diagnostic indicating that the air flow originating from the intake manifold, A condition for the presence or absence of degradation of the engine or the exhaust system is indicated as being met by obtaining a first intake air flow rate via the mass air flow sensor by rotating the engine in the forward direction without fuel via the motor, and obtaining a second intake air flow rate via the mass air flow sensor by rotating the engine in the reverse direction without fuel via the motor just after rotating the engine in the forward direction without fuel to obtain the first intake air flow rate, and wherein indicating the presence or absence of the degradation involves: comparing the first intake air flow rate with a first baseline intake air flow rate to produce a first result, comparing the second intake air flow rate with the second baseline intake air flow rate to produce a second result, and then comparing the first result with the second result to accurately indicate whether degradation exists in the intake manifold, the engine, or the exhaust system.In a first example of the system, the system further includes: wherein the controller stores additional instructions for: indicating degradation originating from the intake manifold when the first result includes the first intake flow being substantially equal to the first baseline intake flow, but wherein the second result includes the second intake flow being less than the second baseline intake flow; indicating degradation originating from the exhaust system when the first result includes the first intake flow being substantially equal to the first baseline intake flow, but wherein the second result includes the second intake flow being greater than the second baseline intake flow; indicating degradation originating from the engine when the first result includes the first intake flow being less than the first baseline intake flow, and wherein the second result includes the second intake flow being less than the second baseline intake flow; and indicating that there is no degradation originating from the intake manifold, the engine, or the exhaust system when the first result includes the first intake flow being substantially equal to the first baseline intake flow, and wherein the second result includes the second intake flow being substantially equal to the second baseline intake flow. A second example of the system optionally includes the first example and further includes: one or more of a seat load sensor, door sensing technology, and / or an onboard camera, wherein the seat load sensor, door sensing technology, and / or the onboard camera are configured to provide information about occupancy of the vehicle by the vehicle driver and passengers; and wherein the controller stores additional instructions for: obtaining the first baseline intake flow and the second baseline intake flow in the absence of an indication of degradation in the intake manifold, the engine, or the exhaust system; and wherein obtaining the first baseline intake flow, obtaining the first intake flow, obtaining the second baseline intake flow, and obtaining the second intake flow are performed under a condition in which the vehicle is indicated as being unoccupied.

[0158] It should be noted that the exemplary control and estimation routines included herein can be used with various engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in a non-transitory memory and can be executed by a control system including a controller in combination with various sensors, actuators and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies (such as event-driven, intermittently driven, multi-tasking, multi-threading, etc.). Thus, the various actions, operations and / or functions shown may be performed in the order shown, in parallel, or in some cases, omitted. Similarly, the 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 may be repeatedly performed depending on the specific strategy used. In addition, the described actions, operations and / or functions may graphically represent code to be programmed into the non-transitory memory of a computer-readable storage medium in the engine control system, wherein the described actions are implemented by executing the instructions in combination with an electronic controller in a system including various engine hardware components.

[0159] It should be understood that the configurations and routines disclosed herein are exemplary in nature, and these specific embodiments should not be considered limiting, as many variations are possible. For example, the above technology can be applied to V-6, inline-4, inline-6, V-12, opposed-4, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or properties disclosed herein.

[0160] The following claims particularly point out certain combinations and subcombinations believed to be novel and non-obvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amendment of the present claims or by presentation of new claims in this or a related application. Such claims, whether broader, narrower, the same, or different in scope than the original claims, are also deemed to be included within the subject matter of the present disclosure.

[0161] According to the present invention, a method is provided, comprising: rotating an engine of a vehicle in a forward direction and a reverse direction without adding fuel to obtain a first intake air flow rate and a second intake air flow rate in an intake duct of the engine, respectively; and indicating a degradation source originating from one of the engine, the intake manifold of the engine, or the exhaust system of the engine based on both the first air flow rate and the second air flow rate.

[0162] According to one embodiment, the above invention is further characterized in that before rotating the engine in the forward direction and the reverse direction without fuel to obtain the first intake flow rate and the second intake flow rate, a set of baseline comparison data is obtained, which includes rotating the engine in the forward direction and the reverse direction without fuel to obtain the first baseline intake flow rate and the second baseline intake flow rate; and wherein, rotating the engine in the forward direction and the reverse direction without fuel is performed via a motor powered by a battery.

[0163] According to one embodiment, the above invention is further characterized in that obtaining the first baseline intake flow rate and the second baseline intake flow rate includes: rotating the engine in the forward direction and the reverse direction under a set of conditions that are substantially equivalent to the conditions for obtaining the first intake flow rate and the second intake flow rate, respectively, wherein the substantially equivalent set of conditions includes: rotating the engine at a first predetermined speed in the forward direction for a first predetermined duration, rotating the engine at a second predetermined speed in the reverse direction for a second predetermined duration, and controlling a throttle valve positioned in the intake manifold to a predetermined position during the rotation of the engine in the forward direction and the reverse direction.

[0164] According to one embodiment, the above invention is further characterized in that rotating the engine in the forward direction and the reverse direction without adding fuel to obtain the first intake flow rate, the second intake flow rate, the first baseline intake flow rate and the second baseline intake flow rate also includes: sealing the intake manifold and the engine from the evaporative emission system of the vehicle; and sealing the engine, the intake manifold and the exhaust system from an exhaust gas recirculation system, which is configured to recirculate at least a portion of the exhaust gas from the engine to the intake manifold under predetermined engine operating conditions.

[0165] According to one embodiment, obtaining the set of baseline comparison data is performed under conditions in which the intake manifold of the engine, the engine, and the exhaust system of the engine are indicated as being free of the degradation source.

[0166] According to one embodiment, in response to the first intake air flow being substantially equal to the first baseline intake air flow and the second intake air flow being substantially equal to the second baseline intake air flow, the engine, the intake manifold, and the exhaust system are indicated as being free of the degradation source.

[0167] According to one embodiment, in response to the first intake air flow rate being substantially equal to the first baseline intake air flow rate, but wherein the second intake air flow rate is less than the second baseline intake air flow rate, the degradation source is indicated as being the intake manifold.

[0168] According to one embodiment, in response to both the first intake air flow rate being less than the first baseline intake air flow rate and the second intake air flow rate being less than the second baseline intake air flow rate, the degradation source is indicated as being the engine.

[0169] According to one embodiment, in response to the first intake air flow being substantially equal to the first baseline intake air flow, but wherein the second intake air flow is greater than the second baseline intake air flow, the degradation source is indicated as being the exhaust system.

[0170] According to the present invention, a method is provided, which comprises: sequentially directing a first airflow through an intake duct of an engine, an intake manifold of the engine, the engine and an exhaust system of the engine under a first condition; sequentially directing a second airflow through the exhaust system, the engine, the intake manifold and the intake duct under a second condition; indicating a first intake flow under the first condition and indicating a second intake flow under the second condition; indicating a first exhaust flow under the first condition; and diagnosing the presence or absence of degradation originating from one of the intake manifold, the engine or the exhaust system based on two or more of the first intake flow, the second intake flow and / or the first exhaust flow.

[0171] According to one embodiment, the above invention is further characterized in that, under a third condition, a first baseline intake flow rate is indicated and a first baseline exhaust flow rate is indicated; under a fourth condition, a second baseline intake flow rate is indicated; and wherein the third condition includes sequentially directing a third airflow through an intake duct of the engine, the intake manifold of the engine, the engine, and the exhaust system of the engine; and wherein the fourth condition includes sequentially directing a fourth airflow through the exhaust system, the engine, the intake manifold, and the intake duct.

[0172] According to one embodiment, the first condition and the third condition include rotating the engine in a forward direction via a motor without fuel to sequentially direct the first airflow through the intake duct, the intake manifold, the engine, and the exhaust system, and wherein the second condition and the fourth condition include rotating the engine in a reverse direction via the motor without fuel to sequentially direct the second airflow through the exhaust system, the engine, the intake manifold, and the intake duct.

[0173] According to one embodiment, directing the first airflow includes directing the first airflow for a first predetermined duration, and wherein directing the third airflow includes directing the third airflow for the first predetermined duration; wherein directing the second airflow includes directing the second airflow for a second predetermined duration, wherein directing the fourth airflow includes directing the fourth airflow for the second predetermined duration, wherein the first predetermined duration is the same as or different from the second predetermined duration; wherein each of the first condition, the second condition, the third condition, and the fourth condition includes controlling a throttle valve positioned in the intake duct of the vehicle to a predetermined opening. position; and wherein each of the first, second, third, and fourth conditions includes sealing an evaporative emissions system from the intake passage, the intake manifold, the engine, and the exhaust system, the evaporative emissions system being configured to capture and store fuel vapor from a fuel system of the vehicle, and wherein each of the first, second, third, and fourth conditions includes sealing the intake passage, the intake manifold, the engine, and the exhaust system from an exhaust gas recirculation system, the exhaust gas recirculation system being configured to recirculate at least a portion of exhaust gas from the engine to the intake manifold.

[0174] According to one embodiment, the above invention is further characterized by indicating the presence of degradation originating from the intake manifold in response to the first intake flow rate being substantially equal to the first baseline intake flow rate, and wherein the first exhaust flow rate is greater than the first baseline exhaust flow rate, and / or wherein the first intake flow rate is substantially equal to the first baseline intake flow rate and wherein the second intake flow rate is less than the second baseline intake flow rate.

[0175] According to one embodiment, the above invention is further characterized by indicating the presence of degradation originating from the exhaust system in response to the first intake flow rate being substantially equal to the first baseline intake flow rate, and wherein the first exhaust flow rate is less than the first baseline exhaust flow rate, and / or wherein the first intake flow rate is substantially equal to the first baseline intake flow rate and wherein the second intake flow rate is greater than the second baseline intake flow rate.

[0176] According to one embodiment, the above invention is further characterized by indicating that degradation originating from the engine is present in response to the first intake flow rate being less than the first baseline intake flow rate, and in response to the first exhaust flow rate being less than the first baseline exhaust flow rate, and / or wherein the first intake flow rate is less than the first baseline intake flow rate and wherein the second intake flow rate is less than the second baseline intake flow rate.

[0177] According to one embodiment, the above invention is further characterized in that the third condition and the fourth condition are performed under conditions in which degradation in the intake manifold, the engine and the exhaust system has not yet been indicated; wherein the first condition, the second condition, the third condition and the fourth condition are all performed under conditions in which the vehicle is not occupied and in which the vehicle is not in motion; and wherein the first intake flow, the first baseline intake flow, the second intake flow and the second baseline intake flow are indicated via a mass air flow sensor positioned in the intake manifold of the engine, and wherein the first exhaust flow and the first baseline exhaust flow are indicated via a differential pressure sensor positioned in the exhaust system.

[0178] According to the present invention, a system for a vehicle is provided, which has: an engine system including an intake manifold, an exhaust system and an engine; a mass air flow sensor, the mass air flow sensor being positioned in the intake manifold; a motor, the motor being capable of rotating the engine without fuel; and a controller storing instructions in a non-transitory memory, which, when executed, causes the controller to: obtain a first baseline intake air flow via the mass air flow sensor by rotating the engine in a forward direction without fuel via the motor, and obtain a second baseline intake air flow via the mass air flow sensor by rotating the engine in a reverse direction without fuel via the motor just after the engine is rotated in the forward direction without fuel to obtain the first baseline intake air flow; and in response to an indication for performing engine system diagnostics to indicate an intake air flow from the intake manifold. A condition for the presence or absence of degradation of the intake manifold, the engine, or the exhaust system is indicated as being met by obtaining a first intake air flow rate via the mass air flow sensor by rotating the engine in the forward direction via the motor without fuel, and just after rotating the engine in the forward direction without fuel to obtain the first intake air flow rate, obtaining a second intake air flow rate via the mass air flow sensor by rotating the engine in the reverse direction via the motor without fuel, and wherein indicating the presence or absence of the degradation involves: comparing the first intake air flow rate with a first baseline intake air flow rate to produce a first result, comparing the second intake air flow rate with the second baseline intake air flow rate to produce a second result, and then comparing the first result with the second result to accurately indicate whether degradation is present in the intake manifold, the engine, or the exhaust system.

[0179] According to one embodiment, the controller stores additional instructions for: indicating degradation originating from the intake manifold when the first result includes the first intake air flow being substantially equal to the first baseline intake air flow, but wherein the second result includes the second intake air flow being less than the second baseline intake air flow; indicating degradation originating from the exhaust system when the first result includes the first intake air flow being substantially equal to the first baseline intake air flow, but wherein the second result includes the second intake air flow being greater than the second baseline intake air flow; indicating degradation originating from the engine when the first result includes the first intake air flow being less than the first baseline intake air flow and wherein the second result includes the second intake air flow being less than the second baseline intake air flow; and indicating the absence of degradation originating from the intake manifold, the engine, or the exhaust system when the first result includes the first intake air flow being substantially equal to the first baseline intake air flow and wherein the second result includes the second intake air flow being substantially equal to the second baseline intake air flow.

[0180] According to one embodiment, the above invention is further characterized by one or more of a seat load sensor, door sensing technology and / or an onboard camera, wherein the seat load sensor, door sensing technology and / or the onboard camera are configured to provide information about the occupancy of the vehicle by the vehicle driver and passengers; and wherein the controller stores additional instructions for: obtaining the first baseline intake flow rate and the second baseline intake flow rate under conditions where there is no indication of degradation in the intake manifold, the engine or the exhaust system; and wherein obtaining the first baseline intake flow rate, obtaining the first intake flow rate, obtaining the second baseline intake flow rate and obtaining the second intake flow rate are performed under conditions where the vehicle is indicated as being unoccupied.

Claims

1. A method for a vehicle, comprising: rotating an engine of an engine system of the vehicle in a forward direction and a reverse direction without adding fuel to obtain a first intake air flow rate and a second intake air flow rate in an intake passage of the engine, respectively, wherein the engine system includes an intake manifold, an exhaust system, and the engine, the engine including a cylinder having an intake valve and an exhaust valve; Before rotating the engine in the forward direction and the reverse direction without fuel to obtain the first intake air flow rate and the second intake air flow rate, obtaining a set of baseline comparison data, which includes rotating the engine in the forward direction and the reverse direction without fuel to obtain a first baseline intake air flow rate and a second baseline intake air flow rate; as well as A source of degradation originating from one of the engine, the intake manifold of the engine system, or the exhaust system of the engine system is indicated based on both a comparison of the first intake air flow rate and the first baseline intake air flow rate and a comparison of the second intake air flow rate and the second baseline intake air flow rate.

2. The method of claim 1, wherein: Rotating the engine in the forward direction and the reverse direction without fuel is performed via a motor powered by a battery.

3. The method of claim 2 , wherein obtaining the first baseline intake air flow rate and the second baseline intake air flow rate comprises: The engine is rotated in the forward direction and the reverse direction under a set of conditions that are equivalent to the conditions for obtaining the first intake air flow rate and the second intake air flow rate, respectively, wherein the equivalent set of conditions includes: rotating the engine in the forward direction at a first predetermined speed for a first predetermined duration, rotating the engine in the reverse direction at a second predetermined speed for a second predetermined duration, and controlling a throttle valve positioned in the intake manifold to a predetermined position during the rotation of the engine in the forward direction and the reverse direction.

4. The method of claim 2, wherein rotating the engine in the forward direction and the reverse direction without fuel to obtain the first intake air flow rate, the second intake air flow rate, the first baseline intake air flow rate, and the second baseline intake air flow rate further comprises: sealing the intake manifold and the engine from an evaporative emissions system of the vehicle; as well as The engine, the intake manifold, and the exhaust system are isolated from an exhaust gas recirculation system configured to recirculate at least a portion of exhaust gas from the engine to the intake manifold under predetermined engine operating conditions.

5. The method of claim 2, wherein obtaining the set of baseline comparison data is performed under conditions wherein the intake manifold of the engine system, the engine, and the exhaust system of the engine system are indicated as being free of the degradation source. 6 . The method of claim 2 , wherein in response to the first intake air flow being equal to the first baseline intake air flow and the second intake air flow being equal to the second baseline intake air flow, the engine, the intake manifold, and the exhaust system are indicated as being free of the degradation source. 7 . The method of claim 2 , wherein in response to the first intake air flow being equal to the first baseline intake air flow, but wherein the second intake air flow is less than the second baseline intake air flow, the degradation source is indicated as being the intake manifold. 8 . The method of claim 2 , wherein the degradation source is indicated as the engine in response to the first intake air flow being less than the first baseline intake air flow and the second intake air flow being less than the second baseline intake air flow. 9 . The method of claim 2 , wherein in response to the first intake air flow being equal to the first baseline intake air flow, but wherein the second intake air flow is greater than the second baseline intake air flow, the degradation source is indicated as being the exhaust system.

10. A system for a vehicle, comprising: An engine system comprising an intake manifold, an exhaust system, and an engine, wherein the engine comprises a cylinder having an intake valve and an exhaust valve; a mass air flow sensor positioned in the intake manifold; a motor capable of rotating the engine without fuel; as well as a controller storing instructions in a non-transitory memory that, when executed, cause the controller to: obtaining a first baseline intake air flow via the mass air flow sensor by rotating the engine in a forward direction via the motor without fuel, and obtaining a second baseline intake air flow via the mass air flow sensor by rotating the engine in a reverse direction via the motor without fuel just after rotating the engine in the forward direction without fuel to obtain the first baseline intake air flow; and In response to conditions for performing engine system diagnostics to indicate the presence or absence of degradation originating from the intake manifold, the engine, or the exhaust system being indicated as being met, obtaining a first intake air flow rate via the mass air flow sensor by rotating the engine in the forward direction via the motor without fuel, and just after rotating the engine in the forward direction without fuel to obtain the first intake air flow rate, obtaining a second intake air flow rate via the mass air flow sensor by rotating the engine in the reverse direction via the motor without fuel, and wherein indicating the presence or absence of the degradation involves: comparing the first intake air flow rate with a first baseline intake air flow rate to produce a first result, comparing the second intake air flow rate with the second baseline intake air flow rate to produce a second result, and then comparing the first result with the second result to pinpoint whether degradation is present in the intake manifold, the engine, or the exhaust system.

11. The system of claim 10 wherein the controller stores further instructions for indicating degradation originating from the intake manifold when the first result includes the first intake air flow being equal to the first baseline intake air flow, but wherein the second result includes the second intake air flow being less than the second baseline intake air flow.

12. The system of claim 10 wherein the controller stores further instructions for indicating degradation originating from the exhaust system when the first result includes the first intake air flow being equal to the first baseline intake air flow, but wherein the second result includes the second intake air flow being greater than the second baseline intake air flow.

13. The system of claim 10, wherein the controller stores further instructions for indicating degradation from the engine when the first result includes the first intake air flow being less than the first baseline intake air flow, and wherein the second result includes the second intake air flow being less than the second baseline intake air flow.

14. The system of claim 10 , wherein the controller stores further instructions for indicating an absence of degradation originating from the intake manifold, the engine, or the exhaust system when the first result includes the first intake air flow being equal to the first baseline intake air flow, and wherein the second result includes the second intake air flow being equal to the second baseline intake air flow.

15. The system of claim 10, further comprising: one or more of seat load sensors, door sensing technology, and / or an onboard camera, wherein the seat load sensors, door sensing technology, and / or the onboard camera are configured to provide information regarding occupancy of the vehicle by a vehicle driver and passengers; and wherein the controller stores further instructions for: obtaining the first baseline intake air flow rate and the second baseline intake air flow rate under conditions where there is no indication of degradation in the intake manifold, the engine, or the exhaust system; and Wherein obtaining the first baseline intake air flow, obtaining the first intake air flow, obtaining the second baseline intake air flow, and obtaining the second intake air flow are performed under the condition that the vehicle is indicated as being unoccupied.

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