Diagnostic Circuit Check

Diagnostic Circuit Check

On-Board Diagnostic System Check - Part 1 Of 2:

On-Board Diagnostic System Check - Part 2 Of 2:

System Electrical Schematic:

Circuit Description:
The OBD System Check is an organized approach to identifying a malfunction created by the electronic engine control system. 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. Understanding the chart and using it correctly will reduce diagnostic time and prevent the unnecessary replacement of good parts.

Test Description:
Numbers below refer to circled numbers on the diagnostic charts.
1. Checks the MIL operation with the ignition switch in the "ON" position.

2. Checks to see if the PCM's normal diagnostic mode is functioning.

3. Checks to see if the PCM's test diagnostic mode is functioning.

4. Checks to see if the vehicle will start.

5. Checks for any DTCs that are stored in the PCM's memory with the engine running.

6. Checks for any DTCs that are stored in the PCM's memory with the engine off.

7. Checks to see if DTC 51 is functioning normally.

8. Checks to see if DTCs that were stored are intermittent malfunctions.