Malfunction Indicator Lamp: Testing and Inspection

The diagnosis found here addresses an inoperative malfunction indicator (Check Engine) lamp condition. If the lamp comes on and stays on with the engine running, refer to Powertrain Management/Computers and Control Systems for diagnosis. If no fuel or emission control systems problem is found, the following procedure will help locate a short or open in the lamp circuit.
1. Disconnect and isolate the battery negative cable. Unplug the PCM wire harness connector C (gray). Install a jumper wire between the malfunction indicator lamp driver circuit cavity of the PCM wire harness connector C and a good ground. Connect the battery negative cable. Turn the ignition switch to the On position. The lamp should light. Remove the jumper wire and the lamp should go off. If OK, refer to the proper Powertrain Diagnostic Procedures in Powertrain Management/Computers and Control Systems to diagnose the PCM. If not OK, go to Step 2.
2. Turn the ignition switch to the Off position. Disconnect and isolate the battery negative cable. Remove the instrument cluster bezel and the cluster assembly Do not unplug the cluster wire harness connectors. Install a jumper wire between the malfunction indicator lamp driver circuit cavity of the cluster printed circuit wire harness connector 1 and a good ground. Connect the battery negative cable. Turn the ignition switch to the On position. The lamp should light. If OK, go to Step 3. If not OK, replace the faulty bulb.
3. Turn the ignition switch to the Off position. Disconnect and isolate the battery negative cable. Unplug the printed circuit wire harness connector 1. Check for continuity between the malfunction indicator lamp driver circuit cavity of the printed circuit wire harness connector 1 and a good ground. There should be no continuity If OK, go to Step 4. If not OK, repair the short circuit as required.
4. Check for continuity between the malfunction indicator lamp driver circuit cavities of the printed circuit wire harness connector 1 and the PCM wire harness connector C. There should be continuity. If not OK, repair the open circuit as required.