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 C0408 02: Rear Axle Coupling Solenoid Valve Short to Ground
DTC C0408 04: Rear Axle Coupling Solenoid Valve Open
DTC C0408 61: Rear Axle Coupling Solenoid Valve Stuck

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Control | C0408 02 | C0408 04 | C0408 04 | C0408 04
Low Reference | C0408 02 | C0408 04 | C0408 04 | C0408 04

Component | Condition | DTCs
--- | --- | ---
Solenoid Valve | Mechanically Stuck | C0408 61

### Circuit/System Description

The rear axle coupling solenoid valve is installed at the rear halfshaft leading to the rear left wheel. The rear differential clutch control module supplies battery voltage to the control circuit and ground to the low reference circuit of the solenoid valve. The solenoid valve is controlled by a pulse width modulation (PWM) signal. The solenoid valve controls the hydraulic pressure to the clutch package of the limited slip differential. The locking level of the limited slip differential depends on the engagement of the clutch package.

### Conditions for Running the DTC

#### C0408 02

• | The ignition is ON.

• | Vehicle is equipped with electronic limited slip differential.

• | The test runs during start up of the rear differential clutch control module.

#### C0408 04

• | The ignition is ON.

• | Vehicle is equipped with electronic limited slip differential.

• | The test runs with a frequency of 200 Hz.

#### C0408 61

• | Vehicle is equipped with electronic limited slip differential.

• | Engine running.

• | Test runs when requested torque is less than 25 N·m (18 lb ft) and the calculated temperature is in the range of 0-120°C (32-248°F).

### Conditions for Setting the DTC

#### C0408 02

A test voltage is applied to the rear axle coupling solenoid valve. An error is detected if the resultant current is greater than the current which corresponds to less than 2.1 Ω resistance in the solenoid valve.

#### C0408 04

The measured current diverges from the nominal value with more than 200 mA for more than 100 ms.

#### C0408 61

The valve is subjected to a current spike that should move the needle physically. An error is detected if the solenoid valve is not moving fast enough and an error counter reaches a threshold.

### Action Taken When the DTC Sets

One or more of the following actions may occur:

• | All-wheel drive (AWD) is disabled

• | Service AWD is displayed on the driver information center.

### Conditions for Clearing the DTC

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

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

### Reference Information

#### Schematic Reference

Rear Axle 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 diagnostic tester information

### Circuit/System Verification

Engine running, observe the scan tool Rear Drive Clutch Status parameter. The reading should be NORMAL when stationary.

### Circuit/System Testing

#### C0408 02 and C0408 04

1. Ignition OFF, inspect for signs of damage of the wire, the solenoid or the housing.

⇒ | If a damage is visible, replace the appropriate component.

2. Disconnect the X2 harness connector at the K47 Rear Differential Clutch Control Module.
3. Test for an infinite resistance between the control circuit terminal W3 at the Q49 Rear Axle Coupling Solenoid Valve and ground.

⇒ | If not within the specified range, test the control circuit and the low reference circuit for a short to ground. If the circuits test normal, replace the Q49 Rear Axle Coupling Solenoid Valve.

4. If the circuits test normal, replace the K47 Rear Differential Clutch Control Module.

#### C0408 61

1. Ignition OFF, inspect for signs of damage of the housing.

⇒ | If a damage is visible, replace the appropriate component.

2. Ignition OFF, replace the Q49 Rear Axle Coupling Solenoid Valve.
3. Ignition ON, verify the DTC does not reset.

⇒ | If the DTC resets, replace the K47 Rear Differential Clutch Control Module.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Limited Slip Differential Clutch Valve Replacement

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