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.

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Control | C0393 0B | 1 | 1 | C0393 0B
Low Reference | -- | 1 | 1 | --
1. Differential lock inoperative

### 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.

### 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 Testing

1. Ignition OFF, disconnect the Q49 Rear Axle Coupling Solenoid Valve.
2. Connect a test lamp between the control circuit terminal A and ground.
3. Ignition ON, command the Rear Differential Clutch Solenoid Valve test ON and OFF with the scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒ | If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K47 Rear Differential Clutch Control Module.

⇒ | If the test lamp is always OFF, test the control circuit for an open / high resistance. If the circuit tests normal, replace the K47 Rear Differential Clutch Control Module.

4. Connect a test lamp between the control circuit terminal A and low reference circuit terminal B.
5. Ignition ON, command the Rear Differential Clutch Solenoid Valve test ON and OFF with the scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒ | If the test lamp is always OFF, test the low reference circuit control circuit for a short to voltage or an open / high resistance. If the circuit tests normal, replace the K47 Rear Differential Clutch Control Module.

6. If all circuits test normal, replace the Q49 Rear Axle Coupling Solenoid Valve.

### 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