Abstract: A method and a system for diagnosing positive crankcase ventilation (PCV) systems are disclosed. In one example, the method diagnoses a PCV system based on a pressure that may be observed during engine cranking. In another example, the PCV system is diagnosed during vehicle driving conditions after the engine exits cranking.

Abstract: Systems and methods for determining degradation of a cylinder deactivation mechanism are described. In one example, engine data generated while an engine is operation with all of its cylinders active is used to correct engine data generated while one or more engine cylinders are deactivated to improve detection of a degraded cylinder deactivation mechanism.

Abstract: Systems and methods for determining degradation of a cylinder deactivation mechanism are described. In one example, engine data generated while an engine is operation with all of its cylinders active is used to correct engine data generated while one or more engine cylinders are deactivated to improve detection of a degraded cylinder deactivation mechanism.

Abstract: Methods and systems are provided for differentiating an exhaust air leak from a catalyst monitor sensor degraded with a slow-response. In one example, a pressure proximate an exhaust system particulate filter less than a threshold pressure may indicate an exhaust air leak and responsive to the indication of the exhaust air leak, the thresholds for monitoring the catalyst monitor sensor response may be adjusted. In this way, the impact of an exhaust air leak on catalyst monitor output may be accounted for so that subsequent monitoring for threshold catalyst may continue to be performed accurately in the presence of an exhaust air leak.

Abstract: Methods and systems are provided for differentiating an exhaust air leak from a catalyst monitor sensor degraded with a slow-response. In one example, a pressure proximate an exhaust system particulate filter less than a threshold pressure may indicate an exhaust air leak and responsive to the indication of the exhaust air leak, the thresholds for monitoring the catalyst monitor sensor response may be adjusted. In this way, the impact of an exhaust air leak on catalyst monitor output may be accounted for so that subsequent monitoring for threshold catalyst may continue to be performed accurately in the presence of an exhaust air leak.

Abstract: A method is provided for monitoring an emission device coupled to an engine. In one example approach, the method comprises: following a deceleration fuel shut-off duration, indicating degradation of the emission device based on an amount of rich products required to cause a sensor to become richer than a threshold. The amount of rich products required may be correlated to an amount of oxygen stored in the emission device.

Abstract: A method is provided for monitoring an emission control device coupled to an engine. In one example approach, the method comprises, following a deceleration fuel shut-off (DFSO) duration, indicating degradation of an emission device based on an amount of rich products required to cause a sensor to become richer than a first threshold, the indicating carried out when DFSO duration is greater than a second threshold. The method also comprises an integration which is based on inlet air-fuel ratio, the integration starting only after a pre-catalyst sensor reaches stoichiometry.

Abstract: A method for monitoring an exhaust gas sensor coupled in an engine exhaust is provided. In one embodiment, the method comprises indicating exhaust gas sensor degradation based on shape of a distribution of extreme values of a plurality of sets of lambda differentials collected during selected operating conditions. In this way, the exhaust gas sensor may be monitored in a non-intrusive manner.

Abstract: Methods and systems are described for evaluating presence of fuel shifts in an engine. In one example, a method comprises indicating a fuel shift based on a time delay of an exhaust gas sensor during an entry into and an exit out of deceleration fuel shut off (DFSO).

Abstract: A method is provided for monitoring an emission control device coupled to an engine. In one example approach, the method comprises, following a deceleration fuel shut-off (DFSO) duration, indicating degradation of an emission device based on an amount of rich products required to cause a sensor to become richer than a first threshold, the indicating carried out when DFSO duration is greater than a second threshold. The method also comprises an integration which is based on inlet air-fuel ratio, the integration starting only after a pre-catalyst sensor reaches stoichiometry.

Abstract: Systems and methods for diagnosing operation of a catalyst are presented. In one example, threshold limits for catalyst variables are adjusted in response to attributes of a catalyst monitor sensor that may vary with sensor age. The catalyst variables may provide insight into whether or not the catalyst is degraded or operating as intended.

Abstract: Methods and systems are provided for converting an asymmetric degradation response of an exhaust gas sensor to a more symmetric degradation response. In one example, a method includes adjusting fuel injection responsive to a modified exhaust oxygen feedback signal from an exhaust gas sensor, the modified exhaust oxygen feedback signal modified by transforming an asymmetric response of the exhaust gas sensor to a more symmetric response. Further, the method may include adjusting one or more parameters of an anticipatory controller of the exhaust gas sensor based on the modified symmetric response.

Abstract: Methods and system are provided for identifying unintended closing (or corking) of a mechanical valve coupled to a fuel tank. If tank vent valve corking is identified during a leak test, fuel tank pressure data collected during the leak test is disregarded and not used to determine a fuel system leak. Instead, a fuel system leak test is repeated to improve reliability of test results.

Abstract: Methods and systems are described for evaluating presence of fuel shifts in an engine. In one example, a method comprises indicating a fuel shift based on a time delay of an exhaust gas sensor during an entry into and an exit out of deceleration fuel shut off (DFSO).

Abstract: Systems and methods for diagnosing operation of a catalyst are presented. In one example, threshold limits for catalyst variables are adjusted in response to attributes of a catalyst monitor sensor that may vary with sensor age. The catalyst variables may provide insight into whether or not the catalyst is degraded or operating as intended.

Abstract: Methods and systems are provided for adjusting an anticipatory controller of an exhaust gas sensor coupled in an engine exhaust. In one embodiment, the method comprises adjusting fuel injection responsive to exhaust oxygen feedback from the anticipatory controller of the exhaust gas sensor and adjusting one or more parameters of the anticipatory controller responsive to a type of oxygen sensor degradation. In this way, the anticipatory controller may be adapted based on the type and magnitude of the degradation behavior to increase performance of the air-fuel control system.

Abstract: A method for monitoring an exhaust gas sensor coupled in an engine exhaust is provided. In one embodiment, the method comprises indicating exhaust gas sensor degradation based on shape of a distribution of extreme values of a plurality of sets of lambda differentials collected during selected operating conditions. In this way, the exhaust gas sensor may be monitored in a non-intrusive manner.

Abstract: A method of monitoring catalyst performance may comprise applying a set of parameter readings for a given sample to a support vector machine to generate a classification output, clustering the set of parameter readings to reduce a number of support vectors, computing a total fuel mass following a deceleration fuel shut-off event and an exhaust gas oxygen sensor switch and indicating catalyst degradation based on the total fuel mass.

Abstract: A method of monitoring an exhaust gas sensor coupled in an engine exhaust is provided. The method comprises indicating exhaust gas sensor degradation based on a difference between a first set of estimated parameters of a rich operation model and a second set of estimated parameters of a lean operation model, the estimated parameters based on commanded lambda and determined lambda values collected during selected operating conditions. In this way, sensor degradation may be indicated with data collected in a non-intrusive manner.

Abstract: Methods and systems are provided for converting an asymmetric degradation response of an exhaust gas sensor to a more symmetric degradation response. In one example, a method includes adjusting fuel injection responsive to a modified exhaust oxygen feedback signal from an exhaust gas sensor, the modified exhaust oxygen feedback signal modified by transforming an asymmetric response of the exhaust gas sensor to a more symmetric response. Further, the method may include adjusting one or more parameters of an anticipatory controller of the exhaust gas sensor based on the modified symmetric response.