Malfunction Indicator Lamp: Testing and Inspection

Malfunction Indicator Lamp (MIL) Diagnosis

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provide an overview of each diagnostic category.

Circuit/System Description

Ignition voltage is supplied directly to the malfunction indicator lamp (MIL). The engine control module (ECM) turns the MIL ON by grounding the MIL control circuit. There should be a steady MIL with the ignition ON and the engine OFF.

Reference Information
Schematic Reference

Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

1. Ignition ON, engine OFF, observe the transmission DTC information with a scan tool. There should be no transmission DTCs set.

• If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code (DTC) List - Vehicle).

2. Command the MIL ON and OFF with a scan tool. The MIL should turn ON and OFF when commanded.
3. Engine idling, command the MIL ON and OFF with a scan tool while observing the following control circuit status parameters:

* MIL Ckt Short Gnd Test Status
* MIL Ckt Open Test Status
* MIL Ckt Short Volts Test Status
Each parameter should display OK or Not Run.

Circuit/System Testing

1. If any other indicators are inoperative, refer to Symptoms - Displays and Gauges (Symptoms - Displays and Gauges).
2. Ignition OFF, disconnect the ECM harness connector X1.
3. Ignition ON, the MIL should not illuminate.

• If the MIL illuminates, test the MIL control circuit terminal 1-X1 for a short to ground. If the circuit test normal, replace the bulb/IPC.

4. Ignition ON, connect a 3 A fused jumper wire between the MIL control circuit terminal 1-X1 and ground. The MIL should illuminate.

• If the MIL does not illuminate, test the MIL control circuit for a short to voltage or an open/high resistance. If the circuit test normal, replace the bulb/IPC.

5. If all circuits test normal, replace the ECM.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Instrument Cluster Bulb Replacement (Notchback) (Service and Repair)
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming