Diagnosis

Diagnosis:

Too much EGR flow at idle, cruise, or cold operation may cause 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 cruise
^ A Tough idle
^ A DTC P0300 (misfire detected) is set

Too little or no EGR flow may allow combustion temperatures to become too high. This could cause the following symptoms:
^ A spark knock
^ An engine overheat
^ An emission test failure
^ A DTC P0401 set
^ Poor fuel economy

An 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 any EGR diagnostic trouble codes are encountered, go to the DTC tables for diagnosis.