Exhaust Gas Recirculation: Testing and Inspection

EGR Diagnosis
Too much EGR flow tends to weaken combustion, causing the engine to run roughly or stop. With too much EGR flow at idle, cruise, or cold operation, any of the following conditions may occur:

^ Engine stops after cold start.

^ Vehicle surge.

^ Engine stops at idle after deceleration or idles rough.

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

Low 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.

^ Emission test failure.

Self-Diagnostics
This powertrain system runs several tests on the EGR system checking for faults in the EGR circuits, the flow of the EGR valve or the controllability of the valve. If any of these checks fail, a PCM Diagnostic Trouble Code (DTC) should set.