Abstract: A system and method for controlling an exhaust gas recirculation (EGR) system in a hybrid vehicle using an intrusive monitor include adjusting EGR flow through an EGR valve based on an average pressure difference between pressure measured from a manifold absolute pressure (MAP) sensor and inferred pressure determined from mass air flow (MAF) into an intake of an engine when engine speed, throttle and camshaft timing position change is below a corresponding threshold. The measured pressure and inferred pressure are determined when the EGR valve is in a closed position and an open position.

Abstract: Methods are provided for performing diagnostic routines in a hybrid vehicle. In one example approach, a method for operating a hybrid vehicle comprises inhibiting engine shutdown and enabling deceleration fuel shut off to perform a monitoring test while a vehicle speed is above a threshold speed.

Abstract: Methods are provided for holding an engine steady during a drive cycle to complete one or more diagnostic routines. The engine may be held steady while an operator torque demand varies if a sufficient number of diagnostic routines need to be completed and are enabled for completion. By holding the engine steady, an accuracy and completion of the diagnostic routines is improved.

Abstract: A system and method for controlling an exhaust gas recirculation (EGR) system in a hybrid vehicle using an intrusive monitor include adjusting EGR flow through an EGR valve based on an average pressure difference between pressure measured from a manifold absolute pressure (MAP) sensor and inferred pressure determined from mass air flow (MAF) into an intake of an engine when engine speed, throttle and camshaft timing position change is below a corresponding threshold. The measured pressure and inferred pressure are determined when the EGR valve is in a closed position and an open position.

Abstract: Methods are provided for performing diagnostic routines in a hybrid vehicle. In one example approach, a method for operating a hybrid vehicle comprises inhibiting engine shutdown and enabling deceleration fuel shut off to perform a monitoring test while a vehicle speed is above a threshold speed.

Abstract: Methods are provided for holding an engine steady during a drive cycle to complete one or more diagnostic routines. The engine may be held steady while an operator torque demand varies if a sufficient number of diagnostic routines need to be completed and are enabled for completion. By holding the engine steady, an accuracy and completion of the diagnostic routines is improved.

Abstract: An EGR fault in an engine is detected by comparing actual MAP values with inferred MAP values, the latter being based on MAF and engine speed. Multiple pairs of inferred and actual MAP, some having low EGR and other having high EGR rate. The two values are expected to deviate at high EGR rate and to be nearly equal at low EGR rate. If no such deviation at high EGR, then a fault is determined. According to the present disclosure, the computation of inferred MAP includes a compensation for flow into the intake through a carbon canister system. Without such compensation, the EGR routine is applied to situations without flow from the canister. Such a limitation caused a problem in HEV vehicles, in which engine operating time is less than typical engine installations. Additionally, the confounding effects of rapid VVT movement are excluded from the computations.

Abstract: An EGR fault in an engine is detected by comparing actual MAP values with inferred MAP values, the latter being based on MAF and engine speed. Multiple pairs of inferred and actual MAP, some having low EGR and other having high EGR rate. The two values are expected to deviate at high EGR rate and to be nearly equal at low EGR rate. If no such deviation at high EGR, then a fault is determined. According to the present disclosure, the computation of inferred MAP includes a compensation for flow into the intake through a carbon canister system. Without such compensation, the EGR routine is applied to situations without flow from the canister. Such a limitation caused a problem in HEV vehicles, in which engine operating time is less than typical engine installations. Additionally, the confounding effects of rapid VVT movement are excluded from the computations.