- Powertrain/On-Board Diagnostic System Check

CIRCUIT DESCRIPTION
The Powertrain On-Board Diagnostic System Check must be the starting point for any driveability complaint diagnosis. Before using this procedure, you should perform a careful visual/physical check of the PCM and engine grounds for being clean and tight. - Visual/Physical Underhood Inspection

The Powertrain On-Board Diagnostic System Check is an organized approach to identifying a problem created by an electronic engine control system malfunction.

DIAGNOSTIC AIDS
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for poor connections or a damaged harness Inspect the PCM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection, and damaged harness.

TEST DESCRIPTION
Number(s) below refer to the Step number(s) on the Diagnostic Table:
1. The MIL should be ON steady with the key ON/ engine OFF. If not, the No Malfunction Indicator Lamp should be used to isolate the malfunction.
2. This test ensures that the PCM is capable transmitting Class II serial data to the DLC and that the Class II data circuit is not open or shorted. If a DLC problem exists, the Data Link Connector Diagnosis should be used to diagnose the condition.
3. If the engine will not start, the Engine Cranks but Does Not Run should be used to diagnose the condition.
4. A scan tool parameter which is not within the typical range may help to isolate the area which is causing the problem.