Diagnostic Aids

Inspect for the following conditions:

• A restricted EGR pipe.
• An EGR valve that shows signs of excessive heat. Check the exhaust system for blockage, possibly a plugged catalytic converter.
• Vacuum restriction to the MAP sensor. A restriction to the MAP sensor can cause the EGR flow test to fail due to insufficient MAP changes being monitored during the test. Inspect for objects blocking the vacuum to the MAP sensor.
• An engine that is running poorly may cause this DTC to set.
• Poor connection or damaged harness. Inspect the wiring harness for damage.
• If the harness appears to be okay, observe the Actual EGR Position display on the scan tool while moving connectors and wiring harnesses 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 22.9 MPH.
• Several deceleration cycles (5-15) will be necessary to run a sufficient number of EGR flow test samples.
• If within the enabling RPM (refer to Conditions For Running DTC), the engine speed drops more than 500 RPM the PCM will reset the test.
• If within the enabling RPM (refer to Conditions For Running DTC), the engine speed increases more than 50 RPM the PCM will reset the test.
• When the PCM commands the EGR valve open, engine speed will drop. If the engine speed drops below 500 RPM, the test will not run.

For an intermittent condition, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.