- Powertrain/On-Board Diagnostic System Check

Powertrain OBD System Check:

MIL, Instrument Panel, And DLC Circuits:

CIRCUIT DESCRIPTION

The Powertrain On-Board Diagnostics (OBD) system check is an organized approach to identifying a problem created by an electronic engine control system malfunction. The Powertrain OBD system check must be the starting point for any driveability complaint diagnosis. The Powertrain OBD system check directs the service technician to the next logical step in diagnosing a complaint. Do not perform this check off no driveability complaint exists. Understanding the table and using it correctly will reduce diagnostic time and prevent the replacement of good parts.

IMPORTANT: This vehicle is equipped with a Powertrain Control Module (PCM) utilizing an Electrically Erasable Programmable Read Only Memory (EEPROM). When diagnostics call for replacement of the PCM, the new PCM must be programmed.

Refer to Powertrain Control Module Replacement.


TEST DESCRIPTION

Number(s) below refer to the Step number(s) on the Diagnostic Chart:

1. The Malfunction Indicator Lamp (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. No Malfunction Indicator Lamp (MIL)

2. This test ensures that the PCM is capable transmitting Class 2 serial data to the Data Link Connector (DLC) and that the Class 2 data circuit is not open or shorted. If a DLC problem exists, the Data Link Connector Diagnosis should be used to diagnose the condition. Data Link Connector Diagnosis

3. If the engine will not start, the Engine Cranks but Does Not Run should be used to diagnose the condition. Engine Cranks, But Will Not Run

4. The scan tool may display transmission DTC(s). Refer to the Powertrain Control Module Diagnosis table for a complete list of DTC(s) supported by this vehicle application. Diagnostic Trouble Code Descriptions

6. A scan tool parameter which is not within the typical range may help to isolate the area which is causing the problem.