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

The malfunction indicator lamp (MIL) is located on the instrument panel cluster (IPC). The MIL informs the driver that an emission system fault has occurred and that the engine control system requires service. The engine control module (ECM) monitors the MIL control circuit for conditions that are incorrect for the commanded state of the MIL. 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 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

Note: Any MIL requesting DTCs that may be set should be diagnosed first.

1. Ignition ON, command the MIL ON and OFF with a scan tool. The MIL should turn ON and OFF as commanded.
2. Ignition ON, command the MIL ON and OFF with a scan tool while observing the following control circuit status parameters:

* MIL Control Circuit Low Voltage Test Status
* MIL Control Circuit Open Test Status
* MIL Control Circuit High Voltage Test Status
Each parameter should toggle between OK and Not Run or Not Run and OK.

Circuit/System Testing

1. Ignition OFF, disconnect the X2 harness connector at the K20 ECM.
2. Ignition ON, the MIL should not illuminate.

• If the MIL is illuminated, test the MIL control circuit terminal 21-X2 for a short to ground. If the circuit tests normal, replace the P16 instrument panel cluster.

3. Connect a 3 A fused jumper wire between the MIL control circuit terminal 21-X2 and ground. The MIL should illuminate.

• If the MIL illuminates, replace the ECM.
• If the MIL does not illuminate, test the MIL control circuit for a short to voltage or an open/high resistance. If the MIL control circuit tests normal, test the instrument cluster ignition circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the instrument panel cluster/bulb.

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 ECM replacement, setup, and programming