EGR Diagnosis

Too much EGR flow tends to weaken combustion, causing the engine to run rough and/or stall. With too much EGR flow at idle, cruise, or cold operation, any of the following conditions may occur:
^ Engine stalls after cold start.
^ Vehicle surge during cruise operation
^ Engine stalls during closed throttle conditions.
^ Rough idle
^ DTC P0300 Misfire Detected

If the EGR valve is stuck open, the engine may not run.

Too little or no EGR flow allows combustion temperatures to get too high during acceleration and load conditions. This could cause:
^ Spark knock/detonation, especially on light acceleration
^ Engine overheating
^ Emission test failure
^ DTC P0401
^ Poor fuel economy

EGR flow diagnosis is included in the DTC P0401 diagnostic table. Pintle position error and control circuit diagnosis is covered in DTCs P0403, P0404, P0405, and P1404. If EGR diagnostic trouble codes are encountered, refer to the appropriate DTC tables for diagnosis.