Systems and procedures for EGR valve diagnostics

Abstract

Method comprising: testing, while an engine is not burning fuel, an exhaust gas recirculation (EGR) valve coupled between an air inlet and an outlet of the engine for deterioration; during the test, rotating the EGR valve to at least one predetermined position and forcing compressed air into the EGR valve; and indicating the presence or absence of deterioration based on one or more pressure readings at the EGR valve; wherein indicating the presence of deterioration includes estimating an initial EGR pressure at the EGR valve when the EGR valve is in the fully closed position, and indicating that the EGR valve is deteriorated in response to the initial EGR pressure being above an initial threshold pressure.

Description

Area The present description generally concerns methods and systems for performing a diagnosis of an exhaust gas recirculation (EGR) valve during a vehicle ignition key off state. General state of the art An exhaust gas recirculation (EGR) system in a vehicle powertrain causes exhaust gases to be recirculated into an engine's intake system with the intention of reducing NOx emissions. However, while NOx is reduced, the exhaust gases inherently contain a dirty environment, including combustion byproducts. Thus, soot and other carbon materials can accumulate in the EGR system over time. For example, an EGR valve located in the EGR channel can become loaded with carbon deposits, which in some cases can cause the EGR valve to deteriorate (e.g., becoming stuck in at least one partially open position or stuck in a fully closed position). Undesirable emissions from a vehicle can increase with a blocked EGR channel or an EGR valve stuck in a closed position. An exemplary approach for diagnosing the operation of an EGR valve is described by Surnilla et al. in US patent US 9,267,453 B2. The EGR valve is forced into a closed position, and a differential pressure across the EGR valve is adjusted to a predetermined pressure via an intake throttle. A leak in the EGR valve can be detected, and the leakage rate can be estimated using a lambda sensor located in the intake manifold downstream of an intercooler. Further prior art is known from German patent applications DE 10 2016 101 210 A1 and DE 10 2012 105 001 A1. However, the inventors of the present invention have recognized potential problems with such systems. For example, performing EGR valve diagnostics by adjusting the intake throttle opening and the EGR valve position during a driving cycle can negatively impact engine performance and the driving experience. In the method demonstrated by Surnilla et al., it may be impossible to distinguish between situations where the EGR valve is stuck in a fully closed position and situations where it is stuck in an open position. Since EGR is primarily provided during vehicle conditions, such as driving at a constant speed on a highway, extended periods of vehicle operation without EGR provision may occur, thus reducing the time available for performing EGR system diagnostics during a driving cycle. Brief description The object of the present invention is therefore to provide improved methods and systems for performing a diagnosis of an exhaust gas recirculation (EGR) valve during a vehicle ignition key off state. This problem is solved by the subject matter of the independent claims. Preferred embodiments are the subject matter of the dependent claims. In one example, the problems described above can be addressed by a procedure for an engine that includes: testing an exhaust gas recirculation (EGR) valve, coupled between an air intake and an exhaust of the engine, for deterioration while the engine is not burning fuel; during the test, rotating the EGR valve to at least one predetermined position and forcing compressed air into the EGR valve; and indicating the presence or absence of deterioration based on one or more pressure readings at the EGR valve. In this way, by forcing compressed air through the EGR channel while the vehicle ignition is off, it is possible to detect EGR valve deterioration. In one example, an EGR valve diagnostic routine can be executed opportunistically during vehicle ignition-key-off states when the engine is not running. The engine can be a turbocharged engine comprising a turbine-driven intake air compressor and an electrically driven intake air compressor (also referred to here as a battery-powered electric booster) that operates selectively to provide additional boost during periods of increased torque demand. During a vehicle-off state, the electric booster can be operated to force pressurized air through the EGR duct. The engine cylinders can be shut down, with the maximum possible number of intake and exhaust valves closed.The diagnostic routine involves commanding the EGR valve to a fully closed position and then estimating a first EGR pressure via a differential pressure sensor coupled to an opening in the EGR channel. The EGR valve can thus be diagnosed as stuck in an open position in response to the first EGR pressure exceeding a first threshold pressure. The diagnostic routine further involves commanding the EGR valve to a fully open position and then estimating a second EGR pressure via the differential pressure sensor. The EGR valve can thus be diagnosed as stuck in a closed position in response to the second EGR pressure falling below a second threshold pressure.Upon detection of EGR valve deterioration, the air-fuel ratio can be adjusted during immediately subsequent engine operation to accommodate any unwanted EGR flow. In this way, by opportunistically utilizing existing engine components, such as an electric booster and a differential pressure sensor, the need for additional sensors and / or equipment for EGR valve diagnostics can be reduced. Passing compressed air through the EGR channel removes accumulated carbon and soot particles, thus cleaning the channel. The technical benefit of performing EGR valve diagnostics with the vehicle ignition off is that the EGR valve's position can be changed without affecting engine performance. By identifying the position in which the EGR valve is stuck, appropriate troubleshooting steps can be taken, reducing the possibility of further engine system deterioration.In general, regularly monitoring the condition of the EGR valve can improve emission quality and fuel efficiency. It is understood that the foregoing summary is provided to present, in simplified form, a selection of concepts that are described in more detail in the detailed description. It is not intended to identify important or essential features of the claimed subject matter, the scope of which is defined solely by the claims following the detailed description. Furthermore, the claimed subject matter is not limited to implementations that overcome the disadvantages mentioned above or in any part of this disclosure. Brief description of the drawings Fig. 1 schematically shows an exemplary vehicle system with an electric booster. Fig. 2 shows a flowchart illustrating a diagnostic routine for diagnosing a deteriorated exhaust gas recirculation (EGR) valve. Fig. 3 shows an exemplary diagnosis of an EGR valve during an engine shutdown state according to the present disclosure. Detailed description The following description concerns systems and methods for diagnosing an exhaust gas recirculation (EGR) valve coupled to an EGR channel contained in an exemplary engine illustrated in Fig. 1. During a vehicle ignition-off state, the vehicle's engine control unit can be configured to execute an exemplary routine to indicate EGR valve deterioration. In one example, a diagnostic routine illustrated in Fig. 2 can be performed. To diagnose the EGR valve, the EGR valve can be instructed to change its opening degree, and the resulting changes in EGR pressure can indicate the EGR valve's condition. Exemplary engine operations to enable EGR valve diagnosis during a vehicle ignition-off state are shown in Fig. 3. Fig. 1 shows a schematic view 101 of a vehicle system 102 with an exemplary engine system 100, which includes an engine 10. In one example, the engine system 100 can be a diesel engine system. In another example, the engine system 100 can be a gasoline engine system. In the illustrated embodiment, the engine 10 is a turbocharged engine coupled to a turbocharger 15, which includes a compressor 114 driven by a turbine 116. Specifically, fresh air is introduced into the engine 10 along the intake duct 42, via the air cleaner 112, and flows to the compressor 114. The compressor can be any suitable intake air compressor, such as a compressor driven by an electric motor or by a drive shaft.In the engine system 10, the compressor is a turbocharged compressor which is mechanically coupled to the turbine 116 via a shaft 19, the turbine 116 being driven by expanding engine exhaust gases. As shown in Fig. 1, the compressor 114 is coupled to the throttle valve 20 via the charge-air cooler (CAC) 118. The throttle valve 20 is coupled to the engine intake manifold 122. The compressed air flows from the compressor through the charge-air cooler 118 and the throttle valve 20 to the intake manifold 122. In the embodiment shown in Fig. 1, the pressure of the air charge within the intake manifold 122 is detected by the manifold air pressure sensor (MAP sensor) 124. The temperature of the ambient air entering the intake duct 42 can be estimated by an intake air temperature sensor (IAT sensor) 51. One or more sensors can be coupled to an inlet of the compressor 114. For example, a temperature sensor 55 can be coupled to the inlet to estimate a compressor inlet temperature, and a pressure sensor 56 can be coupled to the inlet to estimate a compressor inlet pressure. As another example, an ambient humidity sensor 57 can be coupled to the inlet to estimate the humidity of an air charge entering the intake manifold. Other sensors can include, for example, air-fuel ratio sensors, etc. In other examples, one or more of the compressor inlet conditions (such as humidity, temperature, pressure, etc.) can be derived based on engine operating conditions.Additionally, the sensors can estimate the temperature, pressure, humidity, and air-fuel ratio of the air charge mixture, including fresh air, recirculated compressed air, and residual exhaust gases captured at the compressor inlet. A wastegate actuator 91 can be opened to release at least a portion of the exhaust pressure from upstream of the turbine via the wastegate 90 to a point downstream of the turbine. By reducing the exhaust pressure upstream of the turbine, the turbine speed can be reduced, which in turn helps to reduce compressor pumping. To assist the turbocharger 15, an additional intake air compressor, also referred to here as an electric booster 155, can be integrated into the vehicle's propulsion system. The electric booster 155 can be powered by an onboard energy storage device 250, which may include a battery, a capacitor, a supercapacitor, etc. The electric booster may include a compressor driven by an electric motor. Adjusting the operating speed of the electric booster may involve matching the operating speed of the electric motor, which is powered by the onboard energy storage device 250. In one example, the electric booster 155 can be activated in response to a demand for increased wheel torque to quickly provide the desired boost air to the engine while the turbocharger turbine is spooling up. As a result, the increased torque can be achieved without causing turbo lag, which would otherwise have occurred if the electric booster assistance had not been available. In such an example, the electric booster 155 can be switched off or deactivated in response to the turbocharger spooling up to a threshold speed (e.g., 70,000 rpm). Specifically, the operation of the electric booster 155 can be controlled based on command signals (e.g., duty cycle or pulse width signals) received from the vehicle control unit (e.g., the controller 12).For example, the controller can send a signal to actuator 155b of the electric booster, which can switch the electric booster on. In another example, the controller can send a signal to actuator 155b of the electric booster, which can switch the electric booster off. In one example, the actuator of the electric booster can include an electric motor that drives the compression of air. The electric booster 155 can be positioned between a first line 159a and a second line 159b of the electric booster. The first line 159a of the electric booster can fluidically couple the intake duct 42 upstream of the bypass valve 161 of the electric booster to the electric booster 155. The second line 159b of the electric booster can fluidically couple the electric booster 155 downstream of the bypass valve 161 of the electric booster to the intake duct 42. For example, air can be drawn into the electric booster 155 via the first line 159a of the electric booster upstream of the bypass valve 161, and compressed air from the electric booster 155 can exit and be directed to the intake duct 42 via the second line of the electric booster downstream of the bypass valve 161.In this way, compressed air can be directed to the engine intake 122. Under circumstances where the electric booster 155 is switched on to provide boost more quickly than if only the turbocharger 15 were used, it is understood that the bypass valve 161 of the electric booster can be commanded to a closed position while the electric booster 155 is switched on. In this way, intake air can flow through both the turbocharger 15 and the electric booster 155. Once the turbocharger reaches the threshold speed, the electric booster 155 can be switched off and the bypass valve 161 of the electric booster can be commanded to an open position. The intake manifold 122 is coupled to a series of combustion chambers 30 via a series of intake valves (not shown). The combustion chambers are further coupled to the exhaust manifold 36 via a series of exhaust valves (not shown). In the illustrated embodiment, a single exhaust manifold 36 is shown. In other embodiments, however, the exhaust manifold can include a plurality of exhaust manifold sections. Configurations featuring a plurality of exhaust manifold sections can allow exhaust gases from different combustion chambers to be directed to different locations in the engine system. In one embodiment, each of the exhaust and intake valves can be electronically actuated or controlled. In another embodiment, each of the exhaust and intake valves can be actuated or controlled by cams. Regardless of whether actuation is electronic or cam-operated, the timing of the opening and closing of the exhaust and intake valves can be adjusted as required for the desired combustion and emission control performance. The combustion chambers 30 can be supplied with one or more fuels, such as gasoline, alcohol-fuel mixtures, diesel, biodiesel, compressed natural gas, etc., via the injection device 66. The fuel can be supplied to the combustion chambers via direct injection, port injection, throttle body injection, or any combination thereof. Combustion in the combustion chambers can be initiated by spark ignition and / or compression ignition.As shown in Fig. 1, exhaust gas from one or more exhaust manifold sections can be directed to the turbine 116 to drive the turbine. The combined flow from the turbine and the wastegate then flows through the emission control device 170. In one example, the emission control device 170 can be a pre-catalyst. In general, the exhaust aftertreatment device 170 is configured to catalytically treat the exhaust gas stream, thereby reducing the amount of one or more substances in the exhaust gas stream. For example, the exhaust aftertreatment device 170 can be configured to trap NOx from the exhaust gas stream when the exhaust gas stream is lean and to reduce the trapped NOx when the exhaust gas stream is rich. In other examples, the exhaust aftertreatment device 170 can be configured to disproportionate NOx or to selectively reduce NOx using a reducing agent.In other examples, the exhaust aftertreatment device 170 can be configured to oxidize hydrocarbon and / or carbon monoxide residues in the exhaust stream. Different exhaust aftertreatment catalysts with such functionality can be arranged separately or together in washcoats or at other locations within the exhaust aftertreatment stages. In some embodiments, the exhaust aftertreatment stages can include a regenerable soot filter configured to capture and oxidize soot particles in the exhaust stream. An exhaust gas recirculation (EGR) supply channel 180 can be coupled to the exhaust duct 104 upstream of the turbine 116 to provide high-pressure EGR (HPEG) to the engine intake manifold downstream of the compressor 114. The EGR channel 180 can include one or more flow limiting sections (orifices) 21. One or more pressure sensors 22 can be coupled to the flow limiting section 21. In one example, the pressure sensor 22 can be a differential pressure sensor. The differential pressure sensor can be used to determine the pressure of the airflow through the orifice 21. The total volumetric flow rate through the EGR channel 180 can be estimated based on the pressure of the airflow through the orifice 21. An EGR valve 152 can be coupled to the EGR channel 180 at the connection point of the EGR channel 180 and the intake channel 42.The EGR valve 152 can be opened to allow a controlled amount of exhaust gas to the compressor outlet for desired combustion and emission control performance. The EGR valve 152 can be configured as a continuously variable valve or as an on / off valve. In further embodiments, the engine system can include a low-pressure EGR (LP-EGR) flow path, wherein exhaust gas is drawn in downstream from the turbine 116 and returned upstream from the compressor 114 to the engine intake manifold. One or more sensors can be connected to EGR channel 180 to provide details regarding the composition and condition of the EGR. For example, a temperature sensor can be provided to determine the EGR temperature, a humidity sensor can be provided to determine the moisture or water content of the EGR, and an air-fuel ratio sensor can be provided to estimate the air-fuel ratio of the EGR. Alternatively, EGR conditions can be derived from the one or more temperature, pressure, humidity, and air-fuel ratio sensors connected to the compressor inlet. When exhaust gas is recirculated via the EGR channel 180, soot and other carbon materials can accumulate in the EGR system over time, for example, in the opening 21. As an example, an EGR valve 152 can become loaded with coking, which in some cases can cause the EGR valve to deteriorate (e.g., sticking in at least one partially open position or stuck in a fully closed position). A diagnostic routine for the EGR valve 152 can be performed periodically or opportunistically when the vehicle ignition is off. While the engine is not burning fuel, compressed air can be forced through the EGR channel by operating the electric booster 155 via the electric booster actuator 155b (electric motor).A first EGR pressure can be estimated when the EGR valve is in the fully closed position, and EGR valve deterioration can be indicated as a response to the first EGR pressure being above a first threshold pressure. A second EGR pressure can be estimated when the EGR valve is in the fully open position, and EGR valve deterioration can be indicated as a response to the second EGR pressure being below a second threshold pressure. The absence of EGR valve deterioration can be indicated as a response to the first EGR pressure being substantially equal to the first threshold pressure and the second EGR pressure being substantially equal to the second threshold pressure. Both the first and second EGR pressures can be estimated via the differential pressure sensor 22, which is coupled to an opening 21 in the EGR channel 180.Details of a diagnostic routine for the EGR valve 152 are described in relation to Fig. 2. A variety of sensors, including an exhaust gas temperature sensor 128, an exhaust gas lambda sensor, an exhaust gas flow sensor, and an exhaust gas pressure sensor 129, can be coupled to the main exhaust gas channel 104. The lambda sensor can be a linear lambda sensor or UEGO sensor (universal or wide-range exhaust gas oxygen sensor), a dual-state lambda sensor, or an EGO, HEGO (heated EGO), NOx, HC, or CO sensor. The engine system 100 can further include the control system 14. It is shown that the control system 14 receives information from a variety of sensors 16 (various examples of which are described here) and sends control signals to a variety of actuators 18 (various examples of which are described here). For example, the sensors 16 can include the exhaust gas sensor 126 located upstream of the turbine 116, the MAP sensor 124, the exhaust gas temperature sensor 128, the exhaust gas pressure sensor 129, the compressor inlet temperature sensor 55, the compressor inlet pressure sensor 56, the ambient humidity sensor 57, the IAT sensor 51, the differential pressure sensor 22, an engine coolant temperature sensor, and an EGR sensor. Other sensors, such as additional pressure, temperature, air-fuel ratio, and composition sensors, can be coupled at various points in the engine system 100.In addition, sensors coupled to the outside of the vehicle system, such as the rain sensor (windshield sensor) 130, can be used to estimate the ambient humidity. The actuators 18 can include, for example, the bypass valve 161 of the electric booster, the throttle 20, the actuator 155b of the electric booster, the EGR valve 152, the wastegate 92, and the fuel injection device 66. The control system 14 can include a controller 12. The controller 12 can receive input data from the various sensors, process the input data, and trigger various actuators in response to the processed input data based on an instruction or code programmed therein, which corresponds to one or more routines. In one example, the controller 12 can send a signal to the actuator 155b of the electric booster to actuate the electric booster 155 to allow compressed air to flow through the EGR channel 180 while the vehicle ignition key is off.During operation of the electric booster 155, the control unit 12 can send a signal to the EGR valve 152 to change the position of the EGR valve 152 and to detect a deterioration of the EGR valve 152 based on a corresponding change in the EGR pressure, as estimated via the differential pressure sensor 22. In some examples, the vehicle 102 may be a hybrid vehicle with multiple torque sources available to one or more vehicle wheels 157. In other examples, the vehicle 102 is a conventional vehicle with only one engine or an electric vehicle with only one electric machine. In the example shown, the vehicle 102 includes an engine 10 and an electric machine 52. The electric machine 52 may be an electric motor or an electric motor / generator. The crankshaft of the engine 10 and the electric machine 52 are connected to the vehicle wheels 157 via a transmission 46 when one or more clutches 156 are engaged. In the example shown, a first clutch 156 is provided between the crankshaft and the electric machine 52, and a second clutch 156 is provided between the electric machine 52 and the transmission 46.The control unit 12 can send a signal to an actuator of each clutch 156 to engage or disengage the clutch, thereby connecting or disconnecting the crankshaft from the electric machine 52 and its associated components, and / or connecting or disconnecting the electric machine 52 from the transmission 46 and its associated components. The transmission 46 can be a manual transmission, a planetary gear system, or another type of transmission. The powertrain can be configured in various ways, including as a parallel, series, or series-parallel hybrid vehicle. The electric machine 52 receives electrical power from a traction battery 58 to provide torque to the vehicle wheels 157. The electric machine 52 can also be operated as a generator to provide electrical power for charging the traction battery 58, for example, during braking. In this way, the components from Fig. 1 enable a system for a hybrid vehicle comprising: a vehicle, an engine comprising one or more cylinders, an intake manifold and an exhaust manifold, an intake duct comprising a compressor and a compressed air cooler (CAC) downstream of the compressor, a line coupled to the intake duct downstream of the compressor and upstream of the CAC, the line comprising an electric motor-driven electric booster, a bypass valve of the electric booster coupled at a junction of the intake duct and the line, an exhaust gas recirculation (EGR) duct coupling the exhaust manifold downstream of the compressor to the intake manifold, the EGR duct comprising an EGR valve and an orifice, and a differential pressure sensor coupled to the orifice in the EGR duct.The system further includes a control unit with computer-readable instructions stored in non-transient memory for: operating the electric booster while the vehicle ignition key is off, commanding the EGR valve to a fully closed position, detecting EGR pressure via the differential pressure sensor after the commanded closing of the EGR valve, and indicating that the EGR valve is stuck in an open position in response to the detected EGR pressure exceeding a first threshold pressure. Fig. 2 shows an exemplary method 200 that can be implemented to detect any deterioration of an exhaust gas recirculation (EGR) valve (such as EGR valve 152 in Fig. 1) coupled to an EGR channel (such as EGR channel 180 in Fig. 1). Instructions for executing method 200 and the other methods contained herein can be executed by a controller based on instructions stored in a memory of the controller and in conjunction with signals received from sensors of the engine system, such as those described above with reference to Fig. 1. The controller can use engine actuators of the engine system to adjust engine operation according to the methods described below. In procedure 200, part of section 202 involves determining engine and vehicle operating conditions. These operating conditions may include engine speed, engine load, vehicle speed, pedal position, throttle position, mass airflow rate, air-fuel ratio, engine temperature, EGR pressure, oil temperature, etc. The text proceeds to section 204, where procedure 200 involves determining whether conditions for performing an EGR valve diagnostic are met. Conditions for performing the EGR valve diagnostic routine may include an indication of a low EGR flow, as monitored by a pressure sensor (such as the differential pressure sensor 22) in the EGR channel. For example, an expected amount of EGR flow in the absence of carbon deposits associated with the EGR valve and / or in the EGR channel may be stored in the control unit in the form of a lookup table that includes expected flow rates at various engine speeds and / or other operating conditions. A low EGR flow may include a level of EGR flow that differs from an expected EGR flow for a particular engine operating condition by a threshold value, for example, by more than 5% or more than 10%.The conditions for performing EGR diagnostics can, in one example, include a report of a deteriorated EGR system, which is evidenced, for instance, by a rough idle or, in some cases, a complete stall. In yet another example, conditions for running the EGR valve diagnostic routine can include pre-ignition or misfire, as detected in the engine cylinders via a knock sensor. Furthermore, conditions for running the EGR valve diagnostic routine can include an increase in exhaust NOx content above a threshold (such as 5%), as estimated by a NOx sensor connected to an exhaust emission control device. The fulfillment of conditions may additionally or alternatively include a statement that a threshold period (e.g. 1 day, 2 days, 5 days, 10 days, 15 days, more than 20 days but less than 30 days, etc.) has elapsed since a previous EGR valve diagnosis. If it is determined that the conditions for executing an EGR diagnostic routine are not met, current vehicle operation can be maintained at 206. For example, intake manifold EGR can be provided based on engine dilution requirements. The controller can determine a desired level of EGR based on engine operating conditions, including engine speed, engine load, and engine temperature. The controller can use a lookup table to determine the EGR valve opening, with engine speed, engine load, and engine temperature as inputs and the EGR valve position as the output. In another example, an electric booster (such as the electric booster 155 from Fig. 1) can be operated as needed to provide boost assistance during periods of increased torque demand. The electric booster can be connected to a line parallel to an intake manifold, with the line connected to the intake manifold downstream of an intake compressor and upstream of an intercooler. During conditions in which the boost pressure provided by the operation of the turbocharger (such as intake compressor 114 and exhaust turbine 116 from Fig. 1) is below a desired boost pressure, the electric booster can be operated using energy from an on-board energy storage device (such as energy storage device 250 in Fig. 1) to provide the desired boost.The speed and operating time of the electric booster can be adjusted based on the turbocharger speed and torque demand, as estimated by a pedal position sensor. For example, the speed and operating time of the electric booster can be increased when torque demand increases and the turbocharger speed decreases. Conversely, the speed and operating time of the electric booster can be decreased when torque demand decreases and the turbocharger speed increases. If it is determined that the conditions for performing the EGR valve diagnostics are met, the routine at 208 may include determining whether a vehicle ignition key off state is expected. For example, expecting an ignition key off state might involve releasing the accelerator pedal, followed by applying the brakes to stop the vehicle's propulsion (reducing the vehicle speed to zero). Additionally, the transmission might shift into park in anticipation of the vehicle ignition key off state. The ignition switch might also be turned off. If it is determined that no vehicle ignition key off state is expected, the EGR valve diagnostics at 210 can be postponed until the next vehicle ignition key off state. Current vehicle operating states can continue. If it is determined that a vehicle ignition key off state is expected, it can be inferred that the engine can be shut down. The control unit can send signals to the fuel injectors and spark plugs coupled to the engine cylinders to cut off the fuel supply and spark, respectively. At 212, while the engine is off, the control unit can send a signal to the cam actuators coupled to the intake and exhaust valves of the cylinders to shut down the cylinders in a predetermined first position.The first position can include a position in which the maximum number of intake and exhaust valves are in sealed states, such as at top dead center (TDC) of the compression stroke. In one example, the control unit can send a signal to a starter coupled to the crankshaft to turn the engine over after the fuel supply and ignition spark have been cut off, until the cylinders reach the first position. Then, the starter can be turned off (since the cylinders are now shut down in the first position). Alternatively, the engine can be turned over without fuel by an electric motor (such as the electric motor of a hybrid electric vehicle) until the cylinders reach the first position. Once the engine is shut off, the electric booster can be engaged to force compressed air from the intake manifold, through the EGR channel, to the exhaust manifold.The control unit can send a signal to the electric booster actuator (such as actuator 155b in Fig. 1) to activate the electric booster using energy from the energy storage device coupled to the electric booster. As the ambient air entering the intake manifold flows through the electric booster, the air is pressurized (compressed). The intake throttle opening can be increased to a wide-open position to maximize the amount of air entering the intake manifold. By stopping the engine cylinders in a position where the maximum number of intake and exhaust valves are sealed, a higher proportion of the compressed air can be forced through the EGR channel to the exhaust manifold, while a smaller, remaining proportion of the compressed air can flow through the engine cylinders.The predetermined speed of the electric booster during the diagnostic routine can be lower than the speed of the electric booster when operating, in order to compensate for the lag of the mechanical turbocharger. For example, the speed of the electric booster during the diagnostic routine can be 2500 RPM. By operating the electric booster at a lower speed, power consumption can be reduced; noise levels during operation of the electric booster can also be decreased. At 216, the control unit can send a signal to the actuator coupled to the EGR valve to actuate the EGR valve into a fully closed position. If the EGR valve is already in the fully closed position when the engine is shut down, the valve can remain in this position. After the EGR valve closes, at 218, the pressure of the compressed air flowing through the EGR channel (first EGR pressure P1) can be estimated by a differential pressure sensor (such as pressure sensor 22 in Fig. 1) coupled to an opening in the EGR channel. A decrease in the pressure at the opening (EGR pressure), as estimated by the differential pressure sensor, can be directly proportional to the airflow rate through the EGR valve in the EGR channel. Since the EGR valve has been ordered to the closed position, the airflow from the intake manifold via the EGR to the exhaust manifold may be restricted. At 220, the routine includes determining whether the initial EGR pressure P1 is below a first threshold pressure (threshold_1). As an example, the first threshold pressure can be established via the differential pressure sensor during EGR valve installation. During a vehicle ignition key off state after EGR valve installation, the engine can be in the first position (with the maximum number of intake and exhaust valves sealed), the EGR valve can be closed, and the electric booster can then be operated at the predetermined engine speed to force compressed air through the EGR channel. The EGR pressure can be estimated by the differential pressure sensor and stored in the control unit's memory as the first threshold pressure.For example, if the first threshold pressure is estimated with the EGR valve closed, there may be no significant airflow through the EGR duct and the first threshold pressure may be zero. If it is determined that the first pressure P1 is above the first threshold pressure, it can be deduced that, even if the EGR valve has been commanded to the closed position, there is an airflow through the EGR duct, causing a pressure drop at the EGR duct opening. An airflow through the EGR duct while the EGR valve is closed can be caused by the EGR valve being stuck in an open position or by a leak in the EGR valve. Therefore, code 222 can indicate that the EGR valve is leaking or that the EGR valve is stuck in an open position, even if it has been commanded to close. A diagnostic code, such as a flag, can be set to indicate that the EGR valve is stuck in an open position or is leaking. When compressed air flows through the EGR channel, any particulate deposits on the EGR valve (such as carbon deposits) can be carried away by the airflow, causing the EGR valve to close. Air pressure can then carry the particles from the EGR channel, through the exhaust manifold, and into the atmosphere, thus cleaning the EGR channel. If the EGR valve is stuck open due to a particulate matter deposit, it can move to the required closed position after the particulate matter is removed. When a stuck-open EGR valve is closed by the passage of compressed air, the initial EGR pressure can decrease below the initial threshold pressure. If it is determined that the initial EGR pressure is below the first pressure threshold, it can be deduced that the EGR valve could be actuated into a fully closed position and the compressed air cannot flow through the EGR channel. Therefore, it can be stated at 224 that the EGR valve is neither leaking nor stuck in a fully open position, even if it was commanded to be in a closed position. At 226, the control unit can send a signal to the actuator coupled to the EGR valve to actuate the EGR valve into a fully open position. After the EGR valve opens, at 228, the pressure of the compressed air flowing through the EGR channel (second EGR pressure P2) can be estimated via the differential pressure sensor. Since the EGR valve has been commanded to a fully open position, compressed air can begin to flow from the intake manifold through the EGR channel to the exhaust manifold. At 230, the routine includes determining whether the second EGR pressure P2 is below a second threshold pressure (threshold_2). As an example, the second threshold pressure can be established via the differential pressure sensor during the installation of the EGR valve. During a vehicle ignition switch-off state after the EGR valve installation, the engine can be in the first position (with the maximum number of intake and exhaust valves sealed), the EGR valve can be fully open, and the electric booster can then be operated at the predetermined engine speed to force compressed air through the EGR channel. The EGR pressure can be estimated by the differential pressure sensor and stored in the control unit's memory as the second threshold pressure. Each of the first and second threshold pressures can be estimated within a first threshold period since the EGR valve was installed. For example, the first threshold period could be one day from the EGR valve's installation. Alternatively, the first and second threshold pressures can be estimated within a first threshold distance (of the vehicle) since the EGR valve was installed. For example, the first threshold distance could be 30 miles from the EGR valve's installation. In this example, the second threshold pressure could be higher than the first threshold pressure. In this way, the first threshold pressure and the second threshold pressure are calibrated during an engine shutdown state within a threshold duration after installation of the EGR valve by operating the electric booster, wherein the first threshold pressure is the differential pressure sensor reading with the EGR valve completely closed and the second threshold pressure is the differential pressure sensor reading with the EGR valve completely open. In one example, the routine can also determine whether the difference between the second EGR pressure and the first EGR pressure exceeds a threshold difference. Since the EGR valve is actuated from the fully open position to the fully closed position, compressed air can begin to flow through the EGR channel, causing an increase in EGR pressure. The threshold difference can be the non-zero difference between the second threshold pressure and the first threshold pressure. If it is determined that the second EGR pressure P2 is below the second threshold pressure, it can be deduced that even after the EGR valve opens, the airflow through the EGR channel may not have increased to the expected level (the second threshold pressure). Therefore, code 232 may indicate that the EGR valve is stuck in a closed position or that there is a blockage in the EGR valve. It may also indicate that the EGR valve is deteriorating as a result of the difference between the second and first EGR pressures being below the threshold difference. A diagnostic code, such as a flag, may be set to indicate that the EGR valve is stuck in a closed position or blocked. When compressed air flows through the EGR channel, the air pressure can, for example, force a stuck EGR valve into an open position. The air pressure can also dislodge any particles blocking the EGR valve. If a stuck EGR valve is opened by the passage of compressed air, the secondary EGR pressure can rise above the secondary threshold pressure. Upon detection that the EGR valve is malfunctioning, such as being stuck in a fully closed position, stuck in an open position, or leaking, a desired level of engine dilution cannot be achieved by supplying the required amount of EGR during immediately subsequent engine operation. Engine operating parameters can be adjusted to compensate for the lower than desired amount of EGR (if the EGR valve is stuck in a closed position) or higher than desired amount (if the EGR valve is stuck in an open position) supplied to the engine intake. For example, at 234, the air-fuel ratio can be adjusted during immediately subsequent engine operation to account for the EGR flow.If a leaking EGR valve results in the engine cylinders receiving a higher than desired volume of EGR, the control unit can, in one example, send a signal to the actuator coupled to the intake throttle valve to increase the throttle valve opening, adjusting the air-fuel ratio towards a substoichiometric ratio. Conversely, if a blocked EGR valve results in the engine cylinders receiving a lower than desired volume of EGR, the control unit can, in another example, send a signal to the actuator coupled to the fuel injectors to increase the fuel injection pulse width, adjusting the air-fuel ratio towards a superstoichiometric ratio.If, at step 230, it is determined that the second EGR pressure is above the second threshold pressure, or that the difference between the second and first EGR pressures is above the threshold difference, it can be deduced that the compressed air flows through the EGR valve without any restrictions. Therefore, at step 236, it can be indicated that the EGR valve is not stuck in a closed position and is moving to the fully open position as commanded. At step 238, the diagnostic routine is complete, and the electric booster no longer needs to rotate. The control unit can send a signal to the electric booster actuator to stop the electric booster's rotation, and the engine can be returned to a shutdown state. In this way, in a first state, an exhaust gas recirculation (EGR) valve positioned in an EGR channel can be closed, allowing compressed air to pass through the EGR channel, and the EGR valve can be described as being stuck open in response to a pressure change in the EGR channel. In a second state, the EGR valve can be opened, allowing compressed air to pass through the EGR channel, and the EGR valve can be described as being stuck closed in response to the absence of a pressure change in the EGR channel. In the first state, the EGR valve is in an open position when the vehicle ignition key is switched off, and in the second state, the EGR valve is in a closed position when the vehicle ignition key is switched off.The presence of a pressure change in the EGR channel can include a change in pressure at an opening in the EGR channel that exceeds a threshold value after the EGR valve has closed, and the absence of a pressure change in the EGR channel can include a change in pressure at the opening in the EGR channel that is below a threshold value after the EGR valve has opened. Fig. 3 shows an exemplary time axis 300, illustrating the diagnosis of an exhaust gas recirculation (EGR) valve (such as the EGR valve 152 in Fig. 1). The EGR valve is coupled to an EGR channel, which is configured to route at least a portion of the exhaust gas from the outlet to the inlet. The horizontal (x-axis) represents time, and the vertical markers t1-t4 indicate key points in the EGR valve diagnostic routine. The first curve, line 302, shows a variation in vehicle speed over time. The second curve, line 304, shows the operating speed of an electric booster (such as electric booster 155 in Fig. 1). The third curve, line 306, shows the degree of opening of the EGR valve. The fourth curve, line 308, shows an EGR pressure as estimated by a differential pressure sensor (such as pressure sensor 22 in Fig. 1) coupled to an opening in the EGR channel. The dashed line 309 shows a first threshold pressure, and the dashed line 310 shows a second threshold pressure.The first threshold pressure is established when the EGR valve is installed by passing compressed air through the EGR duct with the EGR valve in the fully closed position. The second threshold pressure is established when the EGR valve is installed by passing compressed air through the EGR duct with the EGR valve in the fully open position. Both the first and second threshold values ​​are estimated via the differential pressure sensor. The fourth curve, the dashed lines 314 and 316, show markings indicating deterioration of the EGR valve. Before time t1, the vehicle is driven using engine torque. The electric booster is activated to provide the desired boost pressure. The EGR valve can be opened to allow exhaust gas to be recirculated to the intake manifold. The degree of EGR valve opening is based on engine operating parameters, including engine speed, engine load, and engine temperature. The control unit estimates the EGR valve opening degree using a lookup table, with engine speed, engine load, and engine temperature as inputs and the EGR valve opening degree as output. The EGR pressure is directly proportional to the EGR valve opening and the corresponding volume of EGR flowing through the EGR channel. Since no EGR valve deterioration is detected, the indicator remains in the off position. At time t1, the vehicle is stopped (ignition key switched off). Since engine torque is no longer required for vehicle operation, the operation of the electric booster can also be stopped. Between times t1 and t2, the vehicle is not driven using engine torque and / or machine torque. Because the vehicle is not in operation, the engine does not run combustion and EGR is no longer supplied. Since EGR no longer flows through the EGR channel, the EGR pressure drops to zero. At time t2, after a threshold duration has elapsed since the vehicle ignition key was switched off (the time between time t1 and t2), the EGR valve diagnostics are initiated. The control unit sends a signal to the electric booster actuator to rotate the electric booster. During the diagnostic routine, the electric booster operates at a speed below the speed at which it is used to provide boost (such as before time t1). Additionally, at time t2, the control unit sends a signal to the actuator connected to the EGR valve to actuate the EGR valve in a fully closed position. When the EGR valve is fully closed, no compressed air from the electric booster flows from the intake manifold through the EGR channel to the exhaust manifold. Therefore, there is no significant change in EGR pressure (from zero) between times t2 and t3.Since the EGR pressure remains below the first threshold pressure of 309, it is deduced that the EGR valve is not leaking or stuck in an open position. However, if there were a leak in the EGR valve, compressed air from the electric booster would flow through the EGR duct and the EGR valve, even if it were actuated to a fully closed position. Due to the airflow over the leaking EGR valve, the EGR pressure would exceed the first threshold pressure 309. In response to the EGR pressure exceeding the first threshold 309, between time points t2 and t3, marker 314, indicating that the EGR valve is leaking, would be set, and a diagnostic code would be generated. Upon confirmation that the EGR valve is neither leaking nor stuck in an open position, the control unit, at time t3 and continuing the diagnostic routine, sends a signal to the actuator coupled to the EGR valve to actuate the valve into a fully open position. When the EGR valve is fully open, compressed air begins to flow through the EGR channel and the EGR valve, causing a change in the EGR pressure. Due to the airflow through the EGR channel, the EGR pressure (as shown by the dotted line 312) rises above the second threshold pressure 310. Between times t3 and t4, in response to an EGR pressure exceeding the second threshold 310, it is inferred that the EGR valve is neither blocked nor stuck in a closed position. However, if there were a blockage in the EGR valve, or if the EGR valve were stuck in the closed position, the expected volume of compressed air would not pass from the electric booster through the EGR duct and the EGR valve, even if it were actuated to a fully open position. Due to the reduced airflow through the blocked EGR valve, the EGR pressure would fall below the second threshold pressure 310. In response to the EGR pressure being below the first threshold 310, between time points t3 and t4, marker 316, indicating that the EGR valve is stuck in the closed position (blocked), would be set, and a diagnostic code would be generated. At time t4, the diagnostic routine is complete. The control unit sends a signal to the electric booster actuator to stop the electric booster's rotation. The EGR valve is returned to its position prior to the initiation of the diagnostic routine (before time t2). After time t4, the vehicle remains in the ignition-off state, and the electric motor does not rotate. In this way, the position of the EGR valve can be changed, and EGR valve diagnostics can be performed during engine operation without combustion, without affecting engine performance. By identifying the nature of the EGR valve deterioration, the air-fuel ratio can be appropriately adjusted during subsequent engine operation to improve fuel efficiency and emissions. The technical benefit of using existing engine components, such as an electric booster and a differential pressure sensor, for EGR valve diagnostics is that the need for additional sensors and / or equipment for EGR valve diagnostics can be reduced. In general, regularly monitoring the condition of the EGR valve can improve emissions and fuel efficiency. An exemplary procedure comprises: while an engine is not burning fuel, testing an exhaust gas recirculation (EGR) valve coupled between an air intake and an exhaust of the engine for deterioration; during the test, rotating the EGR valve to at least one predetermined position and forcing compressed air into the EGR valve; and indicating the presence or absence of deterioration based on one or more pressure readings at the EGR valve. In any of the preceding examples, additionally or optionally, the EGR valve is coupled to an EGR duct, the EGR duct being configured to route at least a portion of the exhaust gas from the exhaust to the intake.In any or all of the preceding examples, driving the compressed air additionally or optionally includes driving compressed air through the EGR duct by operating an electric booster via an electric motor, the electric booster being coupled to a line parallel to an intake duct, the line being coupled to the intake duct downstream of an intake compressor and upstream of an intercooler. In any or all of the preceding examples, additionally or optionally, the predetermined position includes a fully closed position and a fully open position.In any or all of the preceding examples, indicating the presence of deterioration additionally or optionally involves estimating a first EGR pressure when the EGR valve is in the fully closed position and indicating that the EGR valve is deteriorated in response to the first EGR pressure being above a first threshold pressure. In any or all of the preceding examples, indicating the presence of deterioration additionally or optionally involves estimating a second EGR pressure when the EGR valve is in the fully open position and indicating that the EGR valve is deteriorated in response to the second EGR pressure being below a second threshold pressure, where the second threshold pressure is above the first threshold pressure.In any or all of the preceding examples, indicating the presence of deterioration additionally or optionally includes further indicating that the EGR valve is deteriorated in response to the difference between the second EGR pressure and the first EGR pressure being below a threshold difference. In any or all of the preceding examples, indicating the absence of deterioration additionally or optionally includes indicating that the EGR valve is not deteriorated in response to the first EGR pressure being substantially equal to the first threshold pressure and the second EGR pressure being substantially equal to the second threshold pressure. In any or all of the preceding examples, additionally or optionally, each of the first EGR pressure and the second EGR pressure is estimated from a differential pressure sensor coupled to an orifice in the EGR channel.In any or all of the preceding examples, the first threshold pressure is established upon installation of the EGR valve by passing compressed air through the EGR duct with the EGR valve in the fully closed position, and the second threshold pressure is established upon installation of the EGR valve by passing compressed air through the EGR duct with the EGR valve in the fully open position, with each of the first and second threshold values ​​being estimated via the differential pressure sensor. In any or all of the preceding examples, the method additionally or optionally further comprises, during immediately subsequent engine operation, adjusting the engine's air-fuel ratio in response to an indication of deterioration. Another procedure for an engine comprises: in a first state, closing an exhaust gas recirculation (EGR) valve positioned in an EGR channel, passing compressed air through the EGR channel and indicating that the EGR valve is stuck open in response to the presence of a pressure change in the EGR channel; and in a second state, opening the EGR valve, passing compressed air through the EGR channel and indicating that the EGR valve is stuck closed in response to the absence of the pressure change in the EGR channel.In any one of the preceding examples, additionally or optionally, the EGR channel is coupled between an engine intake and an engine exhaust, the engine powering a vehicle, and for both the first and second operating states, compressed air is routed through an electric motor by operating an electric booster coupled to the intake during a vehicle ignition-key-off state. In any or all of the preceding examples, additionally or optionally, the EGR valve is in an open position during the vehicle ignition-key-off state in the first state, and the EGR valve is in a closed position during the vehicle ignition-key-off state in the second state.In any or all of the preceding examples, additionally or optionally, the presence of a pressure change in the EGR channel involves a change in pressure at an opening in the EGR channel above a threshold value after the EGR valve has closed, and the absence of a pressure change in the EGR channel involves a change in pressure at the opening in the EGR channel below a threshold value after the EGR valve has opened. In any or all of the preceding examples, additionally or optionally, the change in pressure is estimated via a differential pressure sensor coupled to the opening in the EGR channel. In yet another example, a hybrid vehicle system comprises: a vehicle, an engine comprising one or more cylinders, an intake manifold and an exhaust manifold, an intake duct comprising a compressor and a compressed air cooler (CAC) downstream of the compressor, a line coupled to the intake duct downstream of the compressor and upstream of the CAC, wherein the line comprises an electric motor-driven electric booster, a bypass valve for the electric booster coupled at a junction of the intake duct and the line, an exhaust gas recirculation (EGR) duct coupling the exhaust manifold downstream of the compressor to the intake manifold, wherein the EGR duct comprising an EGR valve and an orifice, and a differential pressure sensor coupled to the orifice in the EGR duct.and a controller with computer-readable instructions stored in non-transient memory to: operate the electric booster while the vehicle ignition key is off, command the EGR valve to a fully closed position, detect EGR pressure via the differential pressure sensor after the EGR valve has been commanded to close, and indicate that the EGR valve is stuck in an open position in response to the detected EGR pressure exceeding a first threshold pressure. In any of the above examples, the controller additionally or optionally includes further instructions to: operate the electric booster while the vehicle ignition key is off, command the EGR valve to a fully open position, detect EGR pressure via the differential pressure sensor after the EGR valve has been commanded to open, and indicate that the EGR valve is stuck in the fully closed position.in response to the detected EGR pressure falling below a second threshold pressure. In any or all of the preceding examples, additionally or optionally, each of the first and second threshold pressures is calibrated during an engine shutdown state within a threshold duration following EGR valve installation by operating the electric booster, wherein the first threshold pressure is the differential pressure sensor reading with the EGR valve fully closed and the second threshold pressure is the differential pressure sensor reading with the EGR valve fully open. In any or all of the preceding examples, additionally or optionally, during the vehicle ignition key off state, one or more cylinders are shut off, with the corresponding intake and exhaust valves in closed positions. It should be noted that the exemplary control and estimation routines contained herein can be used with various engine and / or vehicle system configurations. The control procedures and routines disclosed herein can be stored as executable instructions in non-transient memory and executed by the control system, which includes the control unit in combination with the various sensors, actuators, and other engine hardware. The specific routines described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Accordingly, various illustrated actions, operations, and / or functions can be performed in the illustrated sequence or in parallel, or in some cases, omitted.Similarly, the processing sequence is not strictly necessary to achieve the features and advantages of the exemplary embodiments described here, but is provided for the sake of clarity and description. One or more of the illustrated actions, processes, and / or functions can be performed repeatedly, depending on the specific strategy employed. Furthermore, the described actions, processes, and / or functions can graphically represent code to be programmed into non-transient memory of the computer-readable storage medium in the engine control system, with the described actions being executed by carrying out the instructions in a system that includes the various engine hardware components in combination with the electronic control unit. It is understood that the configurations and routines disclosed herein are exemplary and that these specific embodiments are not to be interpreted in a limiting sense, as numerous variations are possible. For example, the technology described above can be applied to V-6, I-4, I-6, V-12, 4-cylinder boxer, and other engine types. The subject matter of this 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. The following claims highlight certain combinations and subcombinations that are considered novel and not obvious. These claims may refer to "one" element, "a first" element, or the equivalent thereof. Such claims are to be understood as including one or more such elements, without requiring or excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by filing new claims in this or a related application.Such patent claims are also considered to be included in the subject matter of the present disclosure, irrespective of whether they have a broader, narrower, the same or a different scope compared to the original patent claims. According to the present invention, a method comprises, while an engine is not burning fuel, testing an exhaust gas recirculation (EGR) valve for deterioration, which is coupled between an air inlet and an outlet of the engine; during the test, rotating the EGR valve to at least one predetermined position and driving compressed air into the EGR valve; and indicating the presence or absence of deterioration based on one or more pressure measurements at the EGR valve. According to one embodiment, the EGR valve is coupled to an EGR channel, the EGR channel being configured to direct at least part of the exhaust gas from the outlet to the air intake of the engine. According to one embodiment, driving the compressed air involves driving compressed air through the EGR channel by operating an electric booster via an electric motor, wherein the electric booster is coupled to a line parallel to the air intake, the line being coupled to the air intake downstream of an intake compressor and upstream of an intercooler. According to one embodiment, the predetermined position includes a completely closed position and a completely open position. According to one embodiment, indicating the presence of deterioration involves estimating a first EGR pressure at the EGR valve when the EGR valve is in the fully closed position, and indicating that the EGR valve is deteriorated in response to the first EGR pressure being above a first threshold pressure. According to one embodiment, indicating the presence of deterioration involves estimating a second EGR pressure at the EGR valve when the EGR valve is in the fully open position, and indicating that the EGR valve is deteriorated in response to the second EGR pressure being below a second threshold pressure, where the second threshold pressure is above the first threshold pressure. According to one embodiment, indicating the presence of deterioration further includes indicating that the EGR valve is deteriorated in response to a difference between the second EGR pressure and the first EGR pressure being below a threshold difference. According to one embodiment, stating the absence of deterioration involves stating that the EGR valve is not deteriorated in response to the fact that the first EGR pressure is substantially equal to the first threshold pressure and the second EGR pressure is substantially equal to the second threshold pressure. According to one embodiment, each of the first EGR pressure and the second EGR pressure is estimated via a differential pressure sensor coupled to an opening in the EGR channel. According to one embodiment, the first threshold pressure is established upon installation of the EGR valve by passing compressed air through the EGR duct with the EGR valve in the completely closed position, and the second threshold pressure is established upon installation of the EGR valve by passing compressed air through the EGR duct with the EGR valve in the completely open position, with each of the first and second threshold values ​​being estimated via the differential pressure sensor. According to one embodiment, the invention is further characterized by adjusting the air-fuel ratio of the engine during immediately subsequent engine operation in response to a indication of the presence of deterioration. According to the present invention, a method comprises, in a first state, closing an exhaust gas recirculation (EGR) valve positioned in an EGR channel, passing compressed air through the EGR channel and indicating that the EGR valve is stuck open in response to the presence of a pressure change in the EGR channel; and in a second state, opening the EGR valve, passing compressed air through the EGR channel and indicating that the EGR valve is stuck closed in response to the absence of a pressure change in the EGR channel. According to one embodiment, the EGR channel is coupled between an inlet of an engine and an outlet of the engine, wherein the engine drives a vehicle, and wherein, for both the first operating state and the second operating state, the compressed air is directed via an electric motor by operating an electric booster coupled to the inlet during a vehicle ignition key off state. According to one embodiment, in the first state the EGR valve is in an open position during the vehicle ignition key off state, and in the second state the EGR valve is in a closed position during the vehicle ignition key off state. According to one embodiment, the presence of a pressure change in the EGR channel includes a change in pressure at an opening in the EGR channel above a threshold value after closing the EGR valve, and the absence of a pressure change in the EGR channel includes a change in pressure at the opening in the EGR channel below a threshold value after opening the EGR valve. According to one embodiment, the change in pressure is estimated via a differential pressure sensor coupled to the opening in the EGR channel. According to the present invention, a hybrid vehicle system is provided, comprising a vehicle; an engine comprising one or more cylinders, an intake manifold, and an exhaust manifold; an intake duct comprising a compressor and a compressed air cooler (CAC) downstream of the compressor; a line coupled to the intake duct downstream of the compressor and upstream of the CAC, the line comprising an electric motor-driven electric booster; a bypass valve for the electric booster coupled at a junction of the intake duct and the line; an exhaust gas recirculation (EGR) duct coupling the exhaust manifold downstream of the compressor to the intake manifold, the EGR duct comprising an EGR valve and an orifice; and a differential pressure sensor coupled to the orifice in the EGR duct.and a control unit with computer-readable instructions stored in non-transient memory for: during operation of the electric booster while the vehicle ignition key is off, commanding the EGR valve to a fully closed position; detecting an EGR pressure via the differential pressure sensor after the commanded closing of the EGR valve; and indicating that the EGR valve is stuck in an open position in response to the detected EGR pressure exceeding a first threshold pressure. According to one embodiment, the control includes further instructions for: operating the electric booster while the vehicle ignition key is off, commanding the EGR valve to a fully open position, detecting an EGR pressure via the differential pressure sensor after the commanded opening of the EGR valve; and indicating that the EGR valve is stuck in the fully closed position in response to the detected EGR pressure being below a second threshold pressure. According to one embodiment, each of the first threshold pressure and the second threshold pressure is calibrated during an engine shutdown state within a threshold duration after installation of the EGR valve by operating the electric booster, wherein the first threshold pressure is the differential pressure sensor reading with the EGR valve completely closed and the second threshold pressure is the differential pressure sensor reading with the EGR valve completely open. According to one embodiment, the above invention is further characterized in that during the vehicle ignition key switch-off state, one or more cylinders are switched off, with corresponding intake and exhaust valves being in closed positions.

Claims

Method comprising: testing, while an engine is not burning fuel, an exhaust gas recirculation (EGR) valve coupled between an air inlet and an outlet of the engine for deterioration; during the test, rotating the EGR valve to at least one predetermined position and forcing compressed air into the EGR valve; and indicating the presence or absence of deterioration based on one or more pressure readings at the EGR valve; wherein indicating the presence of deterioration includes estimating an initial EGR pressure at the EGR valve when the EGR valve is in the fully closed position, and indicating that the EGR valve is deteriorated in response to the initial EGR pressure being above an initial threshold pressure. Method according to claim 1, wherein the EGR valve is coupled to an EGR channel, wherein the EGR channel is configured to direct at least a portion of the exhaust gas from the outlet to the air inlet of the engine. The method according to claim 2, wherein driving the compressed air comprises driving compressed air through the EGR channel by operating an electric booster via an electric motor, wherein the electric booster is coupled to a line parallel to the air inlet, wherein the line is coupled to the air inlet downstream of an intake compressor and upstream of an intercooler. Method according to claim 1, wherein the predetermined position includes a completely closed position and a completely open position. The method of claim 1, wherein indicating the presence of deterioration includes estimating a second EGR pressure at the EGR valve when the EGR valve is in the fully open position, and indicating that the EGR valve is deteriorated in response to the second EGR pressure being below a second threshold pressure, wherein the second threshold pressure is above the first threshold pressure. Method according to claim 5, wherein indicating the presence of deterioration further includes indicating that the EGR valve is deteriorated in response to a difference between the second EGR pressure and the first EGR pressure being below a threshold difference. The method of claim 5, wherein the indication of the absence of deterioration comprises indicating that the EGR valve is not deteriorated in response to the fact that the first EGR pressure is substantially equal to the first threshold pressure and the second EGR pressure is substantially equal to the second threshold pressure. Method according to claim 5, wherein each of the first EGR pressure and the second EGR pressure is estimated via a differential pressure sensor coupled to an opening in the EGR channel. Method according to claim 5, wherein the first threshold pressure is established upon installation of the EGR valve by passing compressed air through the EGR channel with the EGR valve in the completely closed position, and wherein the second threshold pressure is established upon installation of the EGR valve by passing compressed air through the EGR channel with the EGR valve in the completely open position, each of the first threshold and the second threshold being estimated via the differential pressure sensor. The method of claim 1, further comprising, during immediately subsequent engine operation, adjusting the air-fuel ratio of the engine in response to an indication of the presence of deterioration. Hybrid vehicle system comprising: a vehicle; an engine comprising one or more cylinders, an intake manifold and an exhaust manifold; an intake duct comprising a compressor and a compressed air cooler (CAC) downstream of the compressor; a line coupled to the intake duct downstream of the compressor and upstream of the CAC, the line comprising an electric motor-driven electric booster; a bypass valve for the electric booster coupled at a junction of the intake duct and the line; an exhaust gas recirculation (EGR) duct coupling the exhaust manifold downstream of the compressor to the intake manifold, the EGR duct comprising an EGR valve and an orifice; a differential pressure sensor coupled to the orifice in the EGR duct;and a control unit with computer-readable instructions stored in non-transient memory for: operating the electric booster while the vehicle ignition key is off; commanding the EGR valve to a fully closed position; detecting an EGR pressure via the differential pressure sensor after the EGR valve has been commanded to close; and indicating that the EGR valve is stuck in an open position in response to the detected EGR pressure exceeding a first threshold pressure. System according to claim 11, wherein the control includes further instructions for: operating the electric booster while the vehicle ignition key is off; commanding the EGR valve to a fully open position; detecting an EGR pressure via the differential pressure sensor after the commanded opening of the EGR valve; and indicating that the EGR valve is stuck in the fully closed position in response to the detected EGR pressure being below a second threshold pressure. System according to claim 12, wherein each of the first threshold pressure and the second threshold pressure is calibrated during an engine shutdown state within a threshold duration after installation of the EGR valve by operating the electric booster, wherein the first threshold pressure is the differential pressure sensor reading with the EGR valve completely closed and the second threshold pressure is the differential pressure sensor reading with the EGR valve completely open. System according to claim 11, wherein during the vehicle ignition key off state one or more cylinders are switched off, wherein corresponding inlet and outlet valves are in closed positions. Method comprising: in a first state, closing an exhaust gas recirculation (EGR) valve positioned in an EGR channel, passing compressed air through the EGR channel and indicating that the EGR valve is stuck open in response to the presence of a pressure change in the EGR channel, and in a second state, opening the EGR valve, passing compressed air through the EGR channel and indicating that the EGR valve is stuck closed in response to the absence of the pressure change in the EGR channel.

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