Malfunction Indicator Lamp (MIL) Inoperative

Refer to PCM Malfunction Indicator Lamp (MIL) and Data Link Connector (DLC) and PCM Power and Ground.

Diagnostic Chart 1 Of 2:

Diagnostic Chart 2 Of 2:

CIRCUIT DESCRIPTION
The malfunction indicator lamp MIL illuminates if the ignition is ON, and the engine is OFF. Battery ignition voltage is supplied to the MIL. The powertrain control module will turn the MIL ON by grounding the lamp control circuit. The MIL is OFF if the engine is running correctly.

DIAGNOSTIC AIDS
Check for any of the following conditions:
^ Check for a faulty indicator bulb, or for an open in the instrument cluster power circuit if the engine starts and runs OK.
^ Check for a faulty Main Relay if MIL is not ON, and the engine cranks but will not start.
^ Check for a short in the 5-volt reference circuit if the MIL is not ON, and the engine cranks but will not start.
^ Check for a faulty electrical connection to the PCM.

An intermittent malfunction may be caused by a problem in the MIL electrical circuit. Inspect the wiring harness and the components for any of the following conditions:
^ Backed out terminals
^ Improper mating of terminals
^ Broken electrical connector locks
^ Improperly formed terminals or damaged terminals
^ A faulty terminal to wire connections
^ Physical damage to the wiring harness
^ A broken wire inside the insulation
^ Corrosion of electrical connections, of electrical splices, or of electrical terminals

TEST DESCRIPTION
The numbers below refer to the step numbers in the Diagnostic Table.
1. The Powertrain OBD System Check prompts the technician to complete some basic checks and to store the Freeze Frame data on the scan tool, if applicable. This creates an electronic copy of the data that was stored when the fault occurred. The information is stored in the scan tool for later reference.
5. This step will verify if the MIL circuit is the fault or if the PCM is not providing a ground path for the MIL circuit.
7. This step will verify the condition of the MIL control circuit. The PCM is providing the ground for the test light.
10. This step checks for an open in the Ignition Positive Voltage circuits from the main relay. The engine may start and run but there will not be MIL control or serial data if the circuit is open between the last 2 circuit splices before the PCM.
15. This step checks for a short to ground in the PCM 5 volt reference circuit. The MIL will be inoperative and the engine will not start or run if the reference voltage circuit is shorted to ground. Use the 5 volt reference circuit in order to check the circuit wiring, the sensors, and the components for shorts to ground.