Rear Differential Control Module
The Rear Differential Control Module (RDCM) controls the operation of the motor on the Electric Torque Manager (ETM) differential. The RDCM is located in the luggage compartment adjacent to the startup battery. The RDCM is attached to a bracket with 4 nuts. The bracket is secured to the vehicle floor panel with 4 nuts.
The RDCM receives power supply from the Rear Junction Box (RJB) and an ignition signal from the Body Control Module/Gateway Module (BCM/GWM). A connection with the High Speed (HS) Controller Area Network (CAN) chassis systems bus allows the RDCM to communicate with other control modules on the vehicle.
A certain amount of differential slip is required to allow the vehicle to turn corners and to remain stable under control of the Anti-lock Brake System (ABS) control module. The RDCM monitors the driver's demands through the primary vehicle controls and automatically sets the slip torque in the differential. The system is completely automatic and does not require any special driver input.
The differential strategy in the RDCM includes:
- A pre-loading function, increasing locking torque with increased driving torque.
- A slip controller to decrease locking torque for optimum comfort.
The RDCM memorizes the position of the motor using the signals from the motor position sensors, when the ignition is switched OFF.
The RDCM also sends messages via the HS CAN chassis systems bus to inform other control modules on the network the status of the ETM differential. The clutch torque and default mode status are some of the main signals sent out by the RDCM.
If you replace any of these items, you must connect the Jaguar Land Rover approved diagnostic equipment to the vehicle and do a differential self-calibration procedure:
- The RDCM
- The differential locking motor
- The ETM rear differential.
If a fault occurs with the ETM differential, the RDCM, or 1 of the required input signals, the RDCM records a Diagnostic Trouble Code (DTC). When a DTC is recorded, a warning message is displayed on the Instrument Cluster (IC) message center.
The following messages can be displayed:
| MESSAGE | DESCRIPTION | CHIME |
|---|---|---|
| E-DIFF NOT AVAILABLE | Differential temperature has reached the overheat threshold. System deactivated until temperature returns within limits. | Single |
| E-DIFF FAULT | Fault has occurred with the Electric Torque Manager (ETM) differential. System deactivated until fault rectified. | Single |