Diagnostic Aids

Inspect for the following conditions:

• An EGR valve that shows signs of excessive heat. Check exhaust system for blockage, or for a plugged catalytic converter.
• Vacuum restriction to MAP sensor. A restriction to MAP sensor can cause EGR flow test to fail due to insufficient MAP changes being monitored during the test.
• An engine that is running poorly may cause this DTC to set.
• A poor connection or damaged harness. Inspect wiring harness for damage.
• If harness appears to be okay, observe EGR position sensor display on scan tool while moving connectors and wiring harnesses related to EGR valve. A change in display indicates location of malfunction.

In order to verify a repair, clear info with the scan tool and run the EGR flow test keeping the following items in mind:

• PCM will only run EGR flow test during a gradual deceleration.
• PCM will only run EGR test during a closed throttle condition.
• PCM will only run EGR test at vehicle speeds more than 28 MPH.
• As many as 9-12 deceleration cycles will be necessary to run a sufficient number of EGR flow test samples.
• EGR Test Counter displayed on scan tool can be useful in determining that EGR flow test is running and to keep track of number of test samples taken. Counter will increment each time a test sample is taken.