EGR System on-Board Diagnostics

The PCM performs an on-board diagnostic check of the EGR system. The diagnostic system uses the electronic EGR transducer for the system tests.

The diagnostic check activates only during selected engine/driving conditions. When the conditions are met, the PCM energizes the transducer solenoid to disable the EGR. The PCM checks for a change in the heated oxygen sensor signal.

If the air-fuel mixture goes lean, the PCM will attempt to enrichen the mixture. The PCM registers a Diagnostic Trouble Code (DTC) if the EGR system has failed or degraded.
- After registering a DTC, the PCM turns on the malfunction indicator -- indicating the need for service.

If a problem is indicated by the MIL and a DTC for the EGR system is set, check for proper operation of the EGR system.
- Use the System Test, EGR Gas Flow Test and EGR Diagnosis Chart.

If the EGR system tests properly, check the system using a scan tool and the appropriate Powertrain Control System diagnostic procedures.