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) illuminates to inform the driver that an emission system fault has occurred and that the engine control system requires service. Ignition voltage is supplied directly to the MIL and, when the emission system fault occurs, the engine control module (ECM) turns the MIL ON by grounding the MIL control circuit. Under normal operating conditions, the MIL should be ON only when the ignition is ON and the engine is OFF.

Diagnostic Aids

If the condition is intermittent, move the related harnesses and connectors with the ignition ON and the engine OFF, and with the engine operating while monitoring the scan tool MIL control circuit status parameters. The MIL control circuit status parameters will change from OK or Not Run to Malfunction if there is a condition with the circuit or a connection.

Reference Information
Schematic Reference

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

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 Control Module References 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 control circuit status parameters listed below:

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

3. Engine running, command the MIL ON and OFF with a scan tool while observing the control circuit status parameters listed below:

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

Circuit/System Testing

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

1. Ignition OFF, disconnect the X1 harness connector at the K20 ECM.
2. Ignition ON, the MIL should not illuminate.

• If the MIL illuminates, test the MIL control circuit terminal 46-X1 for a short to ground. If the circuit tests normal, replace the P16 instrument cluster.

Note: The MIL is powered by a dedicated ignition voltage circuit.

3. Connect a 3 A fused jumper wire between the MIL control circuit terminal 46-X1 and ground. The MIL should illuminate.

• If the MIL illuminates, replace the K20 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 voltage circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the P16 instrument panel cluster/bulb.

Repair Instructions

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

* Control Module References Control Module References for ECM replacement, setup, and programming
* Instrument Cluster Replacement (Left Hand Drive) Instrument Cluster Replacement (Left Hand Drive)Instrument Cluster Replacement (Right Hand Drive) Instrument Cluster Replacement (Right Hand Drive)