Malfunction Indicator Lamp (MIL) Diagnosis

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) 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. For example, a failure condition exists if the ECM detects low voltage when the MIL is commanded OFF, or high voltage when the MIL is commanded ON.

Reference Information
Schematic Reference

* Instrument Cluster Schematics (Instrument Cluster Schematics)
* Engine Controls Schematics ([1][2]Electrical Diagrams)

Connector End View Reference

Component Connector End Views (Connector End Views By Name)
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, command the MIL ON and OFF with a scan tool. The MIL should turn ON and OFF as commanded.
2. 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 change from OK and Not Run or from Not Run and OK.

3. Operate the vehicle within the Conditions for Running the DTC to verify that the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

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 circuit fuse is open, replace the IPC.

2. Ignition OFF, disconnect ECM X1 harness connector. Ignition ON, the MIL should not illuminate.

• If the MIL is illuminated, test the MIL control circuit terminal listed below for a short to ground. If the circuit tests normal, replace the IPC.

* ECM terminal X1-27 for RPO LE5
* ECM terminal X1-12 for RPO LAT

3. Ignition ON, connect a 3A fused jumper wire between the MIL control circuit terminal listed below and ground. The MIL should illuminate.

* ECM terminal X1-27 for RPO LE5
* ECM terminal X1-12 for RPO LAT

• 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 IPC/bulb.

4. If all circuits/connections test normal, replace the ECM.

Repair Instructions

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

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