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 C0402 02: Transfer Case Solenoid Valve Short to Ground
DTC C0402 04: Transfer Case Solenoid Valve Open
DTC C0402 43: Transfer Case Solenoid Valve EEPROM Incorrect Programming
DTC C0402 4B: Transfer Case Solenoid Valve Calibration Not Learned
DTC C0402 61: Transfer Case Solenoid Valve Stuck

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Control | C0402 02, C0402 04 | C0402 02 | C0402 02 | C0402 02

Component | Condition | DTCs
--- | --- | ---
Solenoid Valve | Mechanically Stuck | C0402 61
Solenoid Valve Rear Differential Clutch Control Module | Calibration EEPROM Error | C0402 43
Calibration not Learned | C0402 4B

### Circuit/System Description

The transfer case solenoid valve is installed at the torque transfer device housing. 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 torque transfer device. The locking level of the torque transfer device depends on the engagement of the clutch package.

### Conditions for Running the DTC

#### C0402 02, C0402 43 and C0402 4B

• | The ignition is ON.

• | The circuits are tested during start up of the rear differential clutch control module.

#### C0402 04

The ignition is ON.

#### C0402 61

• | 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 0-90°C (32-194°F).

### Conditions for Setting the DTC

#### C0402 02

A test voltage is applied to the transfer case solenoid valve. An error is detected if the resultant current is greater than the current which corresponds to less than 2 Ω resistance in the solenoid valve.

#### C0402 04

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

#### C0402 43

The solenoid valve calibration values stored in the rear differential clutch control module EEPROM are invalid or out of bounds.

#### C0402 4B

There are no solenoid valve calibration values stored in the differential clutch control module EEPROM.

#### C0402 61

An error is detected if the solenoid valve is not moving fast enough for several times.

### Action Taken When the DTC Sets

#### C0402 02, C0402 04 and C0402 61

One or more of the following actions may occur:

• | All-wheel drive (AWD) is disabled.

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

#### C0402 43 and C0402 4B

An error record is stored in the rear differential clutch control module. No action will be performed.

### 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

1. Ignition OFF, replace the Q48 Transfer Case Solenoid Valve.
2. Connect the K47 Rear Differential Clutch Control Module.
3. Ignition ON, verify the DTC does not reset.

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

### Repair Instructions

Rear Differential Clutch Control Module Replacement

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