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.

### DTC Descriptor

DTC C0327: Encoder Circuit Malfunction

### Circuit/System Description

The transfer case shift control module has 4 encoder circuits, and each circuit is supplied 12 volts. These 4 circuits are A, B, C, and P, and each circuit runs to a switch located inside the encoder/motor assembly. When a particular encoder circuit is active, the switch is closed, and the 12 volts are grounded by the switch inside the encoder. The transfer case shift control module supplies 12 volts on all the circuits. The module can interpret the location of the transfer case shift position when the circuits are grounded.

This DTC detects a fault when it compares the shift sequence/strategy to a chart located in read only memory (ROM) within the transfer case shift control module. This is accomplished by the module reading the different combinations of encoder signals being grounded while others remain high depending on what mode or range the transfer case is in.

### Conditions for Running the DTC

• | The ignition is ON.

• | The system voltage is 10-16 volts.

### Conditions for Setting the DTC

This DTC sets when the encoder signals does not match the control strategy contained in the transfer case shift control module.

### Action Taken When the DTC Sets

• | All motor activity will stop.

• | All accessory switch mode indicators will be commanded OFF.

• | The SERVICE 4WD indicator will be on until the fault is corrected.

• | If a new mode is requested by the driver with either a current or history DTC , the transfer case control module will only allow a shift to 2WD mode. The transfer case control module will not allow further mode changes.

### Conditions for Clearing the DTC

• | The DTC will set as both current and history.

• | A scan tool must be used in order to clear a DTC.

### Diagnostic Aids

A low battery condition or charging system that is faulty could set this DTC. 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

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Ignition ON, engine OFF, command each mode function switch ON one at a time, on the instrument panel accessory switch. Each mode button indicator light should illuminate.
2. Road test the vehicle in 4LO, 4HI, Neutral, and 2HI. The transfer case should shift into and out of each mode, while operating the vehicle.
3. Operate the vehicle within the conditions for running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records Data.

### Circuit/System Testing

Important: You must perform the Circuit/System Verification before proceeding to Circuit/System Testing.

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

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

3. Ignition ON, measure for 11-13 volts on terminals A, F, G, H, of the transfer case encoder motor connector.

⇒ | If less than the specified range, test the circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the transfer case shift control module.

4. Ignition OFF, disconnect the transfer case shift control module.
5. Using a DMM, verify that no continuity is detected between each channel encoder signal circuit.

⇒ | If continuity is detected between the circuits, repair as necessary.

⇒ | If all circuits test normal, replace the transfer case encoder motor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Transfer Case Encoder Motor Replacement

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