EGR DiagnosticsCrankcase Ventilation System Description

The engine control module (ECM) tests the exhaust gas recirculation (EGR) flow during deceleration by momentarily commanding the EGR valve to open while monitoring the signal of the manifold absolute pressure (MAP) sensor. When the EGR valve is opened, the ECM will expect to see a predetermined increase in MAP. If the expected increase in MAP is not detected, the ECM records the amount of MAP difference that was detected and adjusts a calibrated fail counter towards a calibrated fail threshold level. When the fail counter exceeds the fail threshold level, the ECM will set a DTC.

Normally, the ECM will only allow one EGR Flow Test Count during an ignition cycle. To aid in verifying a repair, the ECM allows 12 EGR Flow Test Counts during the first ignition cycle following a code clear or a battery disconnect. Between 9-12 EGR Flow Test Counts should be sufficient for the ECM to determine adequate EGR flow and pass the EGR flow test. If the ECM detects an EGR flow error, a DTC will set.

The ECM monitors the position of the EGR valve pintle via the EGR position sensor. If the ECM detects a calibrated variance between the desired EGR valve pintle position and actual position for a calibrated amount of time, a DTC will set.

The ECM also monitors the circuits of the EGR valve for electrical faults. If a circuit fault is detected for a calibrated amount of time, a DTC will set.