EGR System Diagnosis (Overview)

Results of Incorrect Operation
With too much EGR flow at idle, cruise, or cold operation, any of the following conditions may occur:

^ The engine stops after a cold start.
^ The engine stops at idle after deceleration.
^ The vehicle surges during cruise.
^ The vehicle idles roughly.

If the EGR valve stays open all of the time, the engine may not idle. A DTC P0401 may set. Refer to DTC P0401 EGR System Flow Insufficient.

Too little or no EGR flow allows the combustion temperatures to get too high during acceleration and load conditions. This could cause the following conditions:

^ Spark knock (detonation)
^ Engine overheating
^ DTC P0401

System Check
The Linear EGR System Check table covers the diagnosis of the EGR system. Refer to EGR System Diagnosis.