Malfunction Indicator Lamp (MIL) Diagnosis

Malfunction Indicator Lamp (MIL) Diagnosis

Diagnostic Instructions

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



Circuit/System Description

Ignition voltage is supplied to the malfunction indicator lamp (MIL). The engine control module (ECM) turns the MIL ON by grounding the MIL control circuit.


Reference Information
Schematic Reference

* Engine Controls Schematics (Electrical Diagrams)
* Instrument Cluster Schematics (Instrument Cluster Schematics)

Connector End View Reference

Component Connector End Views (Connector Views)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

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


Circuit/System Verification

Ignition ON, the MIL should turn ON and OFF when commanded with a scan tool.


Circuit/System Testing

1. Ignition ON, verify that the instrument panel cluster (IPC) warning indicators are illuminated.

• If the IPC warning indicators are not illuminated, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition fuse is open, replace the IPC.

2. Ignition OFF, disconnect connector X1 at the ECM.
3. Ignition ON, verify that the MIL is not illuminated.

• If the MIL is illuminated, inspect the MIL control circuit for a short to ground. If the circuit tests normal, replace the IPC.

4. Ignition ON, verify that the MIL illuminates with a 3A fused jumper between the MIL control circuit (ECM terminal X1-68) and ground.

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




Repair Instructions

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

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