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 C0550 00: Electronic Control Unit (ECU) Performance

### Circuit/System Description

The rear differential clutch control module (CCM) detects an internal malfunction.

### Conditions for Running the DTC

The ignition is ON.

### Conditions for Setting the DTC

An internal CCM malfunction exists.

### Action Taken When the DTC Sets

All wheel drive indicator illuminates.

### Conditions for Clearing the DTC

• | The condition for the DTC is no longer present.

• | The DTC is not detected in 40 consecutive drive cycles.

### Reference Information

#### Schematic Reference

All-Wheel Drive Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

All-Wheel Drive 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

Verify DTC C0550 is not current.

⇒ | If DTC C0550 is current, replace the CCM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for CCM replacement, setup, and programming