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 transfer case motor is a bi-directional, permanent magnet, D.C. motor. Depending on the command received, the transfer case motor can be energized through either the motor control A or motor control B circuit. The ground circuit for the motor is provided by the motor control circuit that is not energized. The motor, through a series of gears, rotates a shaft which moves the range forks to shift the transfer case between the 2HI, 4HI, 4LO, and Neutral ranges.

### 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 both the motor control A circuit ON and OFF. You should here the encoder motor shifting the transfer case.
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 connectors C1 and C2.
2. Verify that a test lamp illuminates between B+ and C1, terminal 1.

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

3. Verify that a test lamp illuminates between B+ and C1, terminal 9.

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

4. Verify that a test lamp illuminates between C1 terminal 8, and ground.

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

5. Ignition ON, verify that a test lamp illuminates between C2 terminal 10 and ground.

⇒ | If the test lamp does not illuminate test the ignition 1 voltage circuit for a short to ground.

6. Ignition OFF, disconnect the transfer case encoder motor electrical connector.
7. Verify that a test lamp illuminate between B+ and terminal E of the transfer case encoder motor electrical connector.

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

8. Ignition OFF, connect C1 and C2 to the transfer case shift control module.
9. Connect a DMM between terminals B and C of the transfer case encoder motor electrical connector.
10. Ignition ON, with a scan tool, command the motor control A circuit ON and OFF. The DMM should display B+ and zero voltage when commanded ON and OFF.

⇒ | If the DMM displays less than B+ when commanded ON, test both circuits for a short to ground or an open/high resistance. If both circuits test normal, replace the transfer case shift control module.

11. Ignition OFF, remove the transfer case encoder motor. Inspect the shift detent lever shaft for a binding condition.

⇒ | If the shift detent lever shaft inspection is normal, replace the transfer case encoder motor.

### Component Testing

1. Ignition OFF, disconnect the transfer case shift control module electrical connector.
2. With a DMM, measure for 2-100 ohms between motor control A and motor control B terminals on the encoder motor.

⇒ | If not with in the specified range, replace the transfer case encoder motor.

3. Ignition OFF, with a DMM, test for continuity between motor control A terminal and ground, an also motor control B terminal and ground, on the transfer case encoder motor.

⇒ | If continuity is detected, replace the transfer case encoder motor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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

• | Transfer Case Encoder Motor Replacement