C0408
DTC C0408
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC C0408 02
- Rear Axle Coupling Solenoid Valve Short to Ground
DTC C0408 04
- Rear Axle Coupling Solenoid Valve Open
DTC C0408 42
- Rear Axle Coupling Solenoid Valve Calibration Not Programmed
DTC C0408 43
- Rear Axle Coupling Solenoid Valve EEPROM Incorrect Programming
DTC C0408 4B
- Rear Axle Coupling Solenoid Valve Calibration Not Learned
DTC C0408 61
- Rear Axle Coupling Solenoid Valve Stuck
Diagnostic Fault Information
Circuit/System Description
The rear differential clutch solenoid valve is mounted on the rear of the differential 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 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, C0408 42, C0408 43 and C0408 4B
* 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 Nm (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
Voltage is applied to the rear differential clutch solenoid valve. An error is detected if the current is greater than the current which corresponds to less than 2.1 ohms resistance in the solenoid valve.
C0408 04
The measured current deviates from the nominal value with more than 200 mA for more than 100 ms.
C0408 42 and C0408 43
The rear differential clutch solenoid valve calibration values stored in the Rear Differential Clutch Control Module EEPROM are invalid or out of range.
C0408 4B
There are no rear differential clutch solenoid valve calibration values stored in the differential clutch control module EEPROM.
C0408 61
An error is detected if the rear differential clutch solenoid valve is not engaging adequately over a predetermined test sequence.
Action Taken When the DTC Sets
One or more of the following actions may occur:
* All-wheel drive (AWD) is disabled
* Service Rear Axle is displayed on the driver information center.
Conditions for Clearing the DTC
* The condition for setting the DTC is no longer present.
* The DTC is not detected in 40 consecutive ignition cycles.
Diagnostic Aids
The rear differential clutch solenoid valve harness and differential clutch pump harness are all one assembly as part of the differential clutch pump. These harnesses should not be repaired and should be replaced if a wiring condition exists.
Reference Information
Schematic Reference
Rear Axle Schematics Electrical Diagrams
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
Description and Operation
Rear Drive Axle Description and Operation Description
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Engine running and vehicle stationary.
2. Verify the scan tool Rear Drive Clutch Status parameter is Temporarily Limited.
• If not Temporarily Limited
Refer to Circuit/System Testing.
• If Temporarily Limited
3. All OK.
Circuit/System Testing
Note: The Q48 Rear Drive Clutch Solenoid Valve is calibrated with and is part of the K47 Rear Differential Clutch Control Module. Both components must be replaced as a matched set.
C0408 02, C0408 04, C0408 42, C0408 43, or C0408 4B
1. Ignition OFF, disconnect the X2 harness connector at the K47 Rear Differential Clutch Control Module.
2. Test for infinite resistance between the control circuit terminal B and ground.
• If less than infinite resistance
1. Disconnect the harness connector at the Q49 Rear Differential Clutch Solenoid Valve.
2. Test for infinite resistance between the control circuit and ground.
• If less than infinite resistance, test or replace the M32 Differential Clutch Pump.
• If infinite resistance
3. Test or replace the Q49 Rear Differential Clutch Solenoid Valve.
• If infinite resistance
3. Test for 2-4 ohms between the control terminal B and the low reference terminal A.
• If not between 2-4 ohms
1. Disconnect the harness connector at the Q49 Rear Differential Clutch Solenoid Valve.
2. Test for less than 2 ohms in the control circuit end to end.
• If 2 ohms or greater, test or replace the M32 Differential Clutch Pump.
• If less than 2 ohms
3. Test for less than 2 ohms in the low reference circuit end to end.
• If 2 ohms or greater, test or replace the M32 Differential Clutch Pump.
• If less than 2 ohms
4. Test or replace the Q49 Rear Differential Clutch Solenoid Valve.
• If between 2-4 ohms
4. Replace the K47 Rear Differential Clutch Control Module.
C0408 61
1. Replace the Q49 Rear Differential Clutch Solenoid Valve.
2. Ignition ON.
3. Verify DTC C0408 61 is not set.
• If the DTC is set
Replace the K47 Rear Differential Clutch Control Module.
• If the DTC is not set
4. All OK.
Component Testing
Static Test
1. Disconnect the harness connector at the Q49 Rear Differential Clutch Solenoid Valve.
2. Test for 2-4 ohms between the control terminal 1 and low reference terminal 2.
• If not between 2-4 ohms
Replace the Q49 Rear Differential Clutch Solenoid Valve.
• If between 2-4 ohms
3. All OK.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Limited Slip Differential Clutch Valve Replacement Limited Slip Differential Clutch Valve Replacement
* Differential Clutch Pump Replacement Differential Clutch Pump Replacement
* Control Module References Control Module References for Rear Differential Clutch Control Module replacement, programming, and setup.