For 1990-2009 cars

### 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.

### Reference Information

#### Schematic Reference

• | Instrument Cluster Schematics

• | Engine Controls Schematics

#### Connector End View Reference

• | Displays and Gages Connector End Views

• | Engine Control Module Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Output Controls

• | Scan Tool Data Definitions

### Circuit/System Verification

Ignition ON, the MIL should turn ON and OFF when commanded with a scan tool.

### 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 connector C1 at the ECM.
3. Ignition ON, verify that the MIL is not illuminated.

⇒ | If the MIL is illuminated inspect the MIL control circuit for a short to ground. If the circuit tests normal, replace the IPC.

4. Ignition ON, verify that the MIL illuminates with a 3A fused jumper between ECM terminal C1-54 and ground.

⇒ | 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 ECM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Control Module References

• | Instrument Cluster Replacement