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 ohm 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 (Connector End Views By Name)
Description and Operation
Rear Drive Axle Description and Operation (Description and Operation)
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 (Programming and Relearning) for scan tool information
Circuit/System Verification
Engine running, observe the scan tool Rear Drive Clutch Status parameter. The scan tool should display TEMPORARILY LIMITED when stationary.
Circuit/System Testing
Important: The rear drive clutch solenoid valve is calibrated with and is part of the rear differential clutch control module. Both components must be replaced as a matched set.
1. Ignition OFF, disconnect the X2 harness connector at the K47 rear differential clutch control module.
2. Test for a infinite resistance between the control circuit terminal 3 and ground.
• If not the specified value, test the control circuit for a short to ground. If a short to ground is present, replace the M32 differential clutch pump/harness assembly. If the circuit tests normal, replace the Q49 rear differential clutch solenoid valve.
3. Test for 2-4 ohm between the control circuit terminal 3 and the ground reference circuit terminal 4.
• If not within the specified range, replace the Q49 rear differential clutch solenoid valve.
4. Replace the K47 rear differential clutch control module.
C0408 61
1. Replace the Q49 rear differential clutch solenoid valve.
2. 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 (Verification Tests) after completing the diagnostic procedure.
* Limited Slip Differential Clutch Valve Replacement ()
* Differential Clutch Pump Replacement (Differential Clutch Pump Replacement)
* Control Module References (Programming and Relearning) for rear differential clutch control module replacement, setup, and programming