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

Each mode button and the neutral position on the accessory switch has an indicator. When the ignition is turn ON, all four indicators light simultaneously as an indicator check. With the ignition ON, the transfer case shift control module grounds the indicator control circuit, corresponding to the mode button selected by the vehicle operator. The transfer case shift control module flashes each indicator after a shift has been requested, and continues to flash until the transfer case shift control module completes the shift.

### 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 4 accessory switch indicators ON, one at a time. All 4 indicators should illuminate.
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 accessory switch electrical connector.
2. Verify that a test lamp illuminates between B+ and terminal H of the accessory switch electrical connector.

⇒ | If the test lamp does not illuminate, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between terminals A and H of the accessory switch connector.

⇒ | If the test lamp does not illuminate, test the ignition 1 voltage circuit for a short to ground or an open/high resistance.

4. Ignition OFF, connect the accessory switch electrical connector.
5. Ignition OFF, disconnect C1 of the transfer case shift control module.
6. Ignition ON, with a 3A fused jumper wire, individually ground C1 terminals 10, 11, 12, and 13 one at a time. Each indicator lamp should illuminate when the control circuit is grounded.

⇒ | If the indicator does not illuminate, test the indicator control circuit for an open/high resistance. If the circuit tests normal, replace the accessory switch.

7. If all circuits test 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

• | Accessory Switch Replacement