Diagnostic Check Operation

On all California vehicles with EGR systems the PCM performs on-board diagnostic checks of the EGR system, when certain operating conditions are met.

^ The PCM energizes the EGR transducer solenoid, disabling the EGR system, and looks for a momentary change in the oxygen sensor signal.

^ If the EGR system fails the diagnostic check, the PCM sets a trouble code in memory, and turns on the malfunction indicator lamp (instrument panel Check Engine lamp), indicating the need for immediate service.

Note: If a problem is indicated by the malfunction indicator lamp and a diagnostic trouble code for the EGR system, check operation of the EGR system. SEE EGR System Test, EGR Gas Flow Test and EGR Diagnosis Chart. If the EGR system tests properly, check the system using a scan tool. See Powertrain Management/Computers and Control Systems/Testing and Inspection/Procedures.