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

The 4 accessory switch indicator lamps are located on the face of the switch. The 2HI, 4HI, and 4LO indicators are contained inside the respective range button. The Neutral indicator is mounted on the face if the accessory switch. With the ignition ON, the transfer case shift control module grounds the indicator control circuit that corresponds to the selected mode. The transfer case shift control module will flash each indicator lamp after a shift has been requested, and continues to flash until the transfer case shift control module can complete the shift. A 12 volt source located in the accessory switch is applied to the 4 mode indicators.

### Diagnostic Aids

A low battery condition or charging system that is faulty could produce this fault. Refer to Battery Inspection/Test and Charging System Test .

### 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 Verification

1. Ignition ON, with a scan tool command all the accessory switch mode indicators OFF. All the mode indicators should turn OFF.
2. If the vehicle passes the Circuit/System Verification, then refer to Testing for Intermittent Conditions and Poor Connections .

### Circuit/System Testing

1. Ignition OFF, disconnect the transfer case shift control module electrical connector.
2. Ignition ON, all four mode indicator lights on the accessory switch should be OFF.

⇒ | If two or more mode indictor lights are ON, test each indictor control circuit for a short to ground. If the circuit tests normal, replace the transfer case shift control module.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control module replacement, setup, and programming