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 Description

The service 4WD indicator is located in the instrument panel cluster (IPC) and shares the common power and ground of the IPC. The transfer case shift control module turns ON or OFF the SERVICE 4WD indicator by sending the IPC a class 2 message.

### Reference Information

#### Schematic Reference

Transfer Case Control Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Transfer Case Description and Operation

#### 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 Testing

1. Ignition OFF, disconnect connectors C1 and C2 of the transfer case shift control module.
2. Ignition ON, the Service 4WD indicator on the IPC should be OFF.

⇒ | If the Service 4WD indicator is ON, repair or replace the IPC.

⇒ | If the Service 4WD indicator is OFF, replace the transfer case shift control module.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Control Module References for transfer case shift control module replacement, setup, and programming.

• | Instrument Cluster Replacement