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 39: Electronic Control Unit (ECU) Performance

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Electronic Control Unit (ECU) Performance | -- | -- | -- | C0550 39

### Circuit/System Description

The coupling control module (CCM) detects an internal malfunction.

### Conditions for Running the DTC

The ignition switch is in the ON position.

### Conditions for Setting the DTC

An internal EBCM malfunction exists.

### Action Taken When the DTC Sets

One or more of the following actions may occur:

• | All Wheel Drive Off (AWD Disabled).

• | Service All Wheel Drive (Service AWD).

### Conditions for Clearing the DTC

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

• | The DTC is not detected in 100 consecutive drive cycles.

### Reference Information

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Scan Tool Data List

### Circuit/System Verification

DTC C0550 will set as result of internal (CCM) circuit failure.

⇒ | Replace the CCM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for CCM replacement, setup, and programming