Diagnostic Aids

Check for an EGR valve that shows signs of excessive heat caused by exhaust system blockage or plugged catalytic converter. Check for vacuum restriction to MAP sensor. Restrictions can cause EGR flow test to fail due to insufficient MAP changes. Check for engine that is running poorly. Check for poor connection or damaged harness. If harness appears okay, observe EGR position sensor display on scan tool while moving connectors and wiring related to EGR valve.

To verify repair, clear info using scan tool and run EGR flow test keeping in mind:

• PCM will only run EGR flow test during a gradual deceleration.
• PCM will only run EGR test during closed throttle condition.
• PCM will only run EGR test at vehicle speeds above 25 MPH.

Several deceleration cycles, typically 9-12, will be necessary to run a sufficient number of EGR flow test samples. EGR test counter displayed on scan tool can be useful to ensure EGR flow test is running and to track number of test samples taken. Counter will increment each time a sample is taken.