Diagnostic Aids
WARNING: This page is about a different car, the 2002 Pontiac Grand Prix, 2002 Chevrolet Malibu, and 2002 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
Check for any of the following conditions:
- 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. Inspect for objects blocking the vacuum to MAP sensor.
- An engine that is running poorly may cause this DTC to set.
- Poor connection or damaged harness. Inspect wiring harness for damage.
- If the harness appears to be okay, observe the EGR position sensor display on the scan tool while moving the connectors and the wiring harnesses that are related to the EGR valve. A change in the display indicates the location of the malfunction.
In order to verify a repair, clear info with the scan tool and run the EGR flow test, keeping the following conditions in mind:
- The PCM will only run the EGR flow test during a gradual deceleration.
- The PCM will only run the EGR test during a closed throttle condition.
- The PCM will only run the EGR test at vehicle speeds above 35 MPH.
- Several deceleration cycles, typically 9-12, will be necessary in order to run a sufficient number of EGR flow test samples.
- The EGR Test Counter displayed on the scan tool can be useful in determining that the EGR flow test is running, and to track the number of test samples taken. The counter will increment each time a test sample is taken.