Intrusive EEGR System Monitor

When EGR is delivered into the intake manifold, intake manifold vacuum is reduced and thus manifold absolute pressure is increased. A manifold absolute pressure (MAP) sensor and inferred manifold absolute pressure 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 mass airflow (MAF) sensor, the monitor also calculates and averages an inferred manifold absolute pressure 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 manifold absolute pressure values are added together and compared to a minimum threshold to determine if a flow concern (P0400) in the EGR system has occurred.