Intrusive EEGR System Monitor

When EGR is delivered into the intake manifold, intake manifold vacuum is reduced and thus manifold absolute pressure (MAP) is increased. A MAP sensor and inferred MAP are used by this monitor to determine how much EGR is flowing. A MAP sensor located in the intake manifold measures the pressure when EGR is being delivered and when EGR is not being delivered. The pressure difference between EGR on and EGR off is calculated and averaged. If the vehicle is equipped with a MAF sensor, the monitor also calculates and averages an inferred MAP value in the above calculation and resulting average. After a calibrated number of EGR on and EGR off cycles are taken, the measured and inferred MAP values are added together and compared to a minimum threshold to determine if a flow concern (P0400) in the EGR system has occurred.