- Powertrain/On-Board Diagnostic System Check

On Board Diagnostic System Check:

Diagnostic Check Circuit:

CIRCUIT DESCRIPTION
The on-board diagnostic system check must be the starting point for any driveability complaint diagnosis. Before using this you should perform a careful visual/physical check of the Powertrain Control Module (PCM) and engine grounds for being clean and tight.

The on-board diagnostic system check is an organized approach to identifying a problem created by an electronic engine control system malfunction because it directs the service technician to the next logical step in diagnosing the complaint.

CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. The Malfunction Indicator Light (MIL) "Service Engine Soon" should be ON steady with the key ON/engine OFF.
2. This test ensures that the PCM is capable of controlling the MIL "Service Engine Soon" and circuit 419 is not shorted to ground.
3. A displayed Tech 1 scanner parameter which is not within the typical range may indicate the area which is causing the problem.