- Powertrain/On-Board Diagnostic System Check

The Diagnostic Circuit Check is an organized approach to identifying a problem created by an electronic engine control system malfunction. It must be the starting point for any driveability complaint diagnosis because it directs the service technician to the next logical step in diagnosing the complaint.

1. Are the on vehicle diagnostics working? If no, you will be referred to an A Chart. Related Tests, Information and Procedures
If yes, go to step 2.

2. Is there a code stored? If yes, go to that code. Testing and Inspection
If no, go to step 3.

3. Compare information on the Serial Data Stream, to Typical Scan Data Values. Scan Tool Testing and Procedures