Exhaust Gas Recirculation (EGR) System Monitor

The EGR system monitor is an on board strategy designed to test the integrity and flow characteristics of the EGR system. The EGR system monitor consists of an electrical and functional test that checks the EGR valve and the EGR system components for correct operation.

After the vehicle has warmed up and normal EGR rates are being commanded by the PCM, the low flow check and high flow check is carried out. The EGR flow diagnostic execute once per drive cycle and are designed to set a DTC when the total mass flow error results in an emissions increase above calibrated level.

The EGR system uses inputs from the CHT sensor, IAT sensor, CKP sensor, MAP sensor, differential pressure feedback EGR sensor and the vehicle speed to provide information about the engines operating conditions to the PCM.

The PCM uses the sensor inputs to determine the desired amount of EGR gas flow and controls the electric EGR valve commanded position to determine if EGR flow is present.

The monitor checks the electric EGR valve circuits for open and shorts. The monitor compares the differential pressure feedback EGR sensor to a calibrated value and the electric EGR valve commanded position to determine if EGR flow is present.

The monitor checks the differential pressure feedback EGR sensor for open and short circuits. The differential pressure feedback EGR sensor hoses are tested for connection and restriction at idle. The PCM commands the EGR valve closed and the monitor tests for the differential pressure feedback EGR sensor to indicate no flow is present. The PCM commands the EGR open and the monitor tests the differential pressure Feedback EGR sensor voltage to indicate flow is present. The stop start option on some vehicles requires the hose tests to be run during off idle conditions.