Malfunction Indicator Lamp: Testing and Inspection

Malfunction Indicator Lamp (MIL) Diagnosis

Diagnostic Instructions

- Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
- Review Strategy Based Diagnosis for an overview of the diagnostic approach.
- 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.

Diagnostic Aids

If the condition is intermittent, move the related harnesses and connectors with the engine operating. Monitor the scan tool Circuit Test Status parameters for the component. The Circuit Test Status parameter will change from OK or Not run to Fault 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

Connector End View Reference

Component Connector End Views

Electrical Information Reference

- Circuit Testing
- Connector Repairs
- Testing for Intermittent Conditions and Poor Connections
- Wiring Repairs

Scan Tool Reference

Control Module References 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, observe each of the MIL Control Circuit Test parameters listed below with a scan tool:
- The MIL Control Circuit Low Voltage Test Status
- The MIL Control Circuit Open Test Status
- The MIL Control Circuit High Voltage Test Status

Each parameter should display OK or Not Run.

Circuit/System Testing

1. Ignition OFF, disconnect the X1 harness connector at the K20 ECM.
2. Ignition ON, the MIL should not illuminate.
3. If the MIL is illuminated, test the MIL control circuit terminal 46 X1 for a short to ground. If the circuit tests normal, replace the P16 instrument panel cluster.
4. Connect a 3 A fused jumper wire between the MIL control circuit terminal 46 X1 and ground. The MIL should turn on.
5. If the MIL illuminates, replace the ECM.
6. 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 OK, test the instrument panel cluster ignition circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the instrument panel cluster\bulb.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- Instrument Cluster Replacement
- Control Module References for replacement, setup, and programming