Malfunction Indicator Lamp (MIL) Diagnosis. Chevrolet Express

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 2008 🢒 Express - AWD 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 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.

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 states 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.

Diagnostic Aids

An intermittent or poor connection at the MIL control circuit at the inline harness connector may cause this DTC to set. Inspect the connector terminals for any condition that may result in excessive resistance. Refer to Testing for Intermittent Conditions and Poor Connections.

Reference Information

Schematic Reference

•	Engine Controls Schematics

•	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

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, command the MIL ON and OFF with a scan tool. The MIL should turn ON and OFF with each command.

Circuit/System Testing

Ignition ON, verify that the IPC warning indicators are illuminated.

⇒	If the IPC warning indicators are not illuminated, test the IPC 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.

Ignition OFF, disconnect the ECM X2 harness connector. Ignition ON, the MIL should not illuminate.

⇒	If the MIL is illuminated, test the MIL control circuit terminal X2-30 for a short to ground. If the circuit tests normal, replace the IPC.

Ignition ON, connect a 3A fused jumper wire between the MIL control circuit terminal X2-30 and ground. The MIL should illuminate.

⇒	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.

If all circuits/connectors test normal, replace the ECM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Instrument Cluster Replacement

•	Control Module References for ECM and ICM replacement, setup, and programming