Diagnosis

Diagnosis:

Too much EGR flow causes any of the following conditions to occur:
^ The engine stalls after a cold start.
^ The engine stalls during closed throttle conditions.
^ The vehicle surges during a cruise condition.
^ A rough idle
^ A DTC P0300, misfire detected

Too little or no EGR flow allows the combustion temperatures to increase. This causes the following symptoms:
^ Spark knock, detonation
^ Engine overheating
^ Emission test failure.
^ DTC P0401
^ Poor fuel economy

The EGR flow diagnosis is included in the DTC P0401 diagnostic table. The EGR pintle position and the EGR valve control circuit diagnosis are covered in DTCs P0404, P0405, and P1404. Go to the appropriate DTC table for diagnosis if an EGR DTC is stored.