Patent ID: 7367188

Claim:
A method for diagnosing a degradation of a first mass flow sensor in an engine, the engine also including a first and second exhaust gas recirculation system, a turbocharger, a first exhaust gas recirculation system (EGR) coupled between the engine intake and exhaust on a high pressure side of the turbocharger, a second EGR coupled between the engine intake and exhaust on a low pressure side of the turbocharger, an EGR valve located in the second EGR, the first mass airflow sensor located in an intake manifold upstream of the second EGR inlet, a second mass airflow sensor located in an intake manifold downstream of the second EGR inlet and upstream of the first EGR inlet and upstream of the turbocharger, the method comprising: adjusting the second EGR valve position to introduce an EGR perturbation; measuring a flow in the inlet of the second EGR using the first mass airflow sensor, said flow including said perturbation; and diagnosing a degradation of the first sensor based on a deviation between an expected flow through the first mass airflow sensor and the measured flow by the first mass airflow sensor.