Bus communication
The XWD control module, abbreviated to RDCM, is connected to the vehicle's P-bus. Its bus messages are used to determine the operating/driving conditions for the vehicle, and accordingly how much drive torque should be transferred to the rear wheels. The control module and control valve are calibrated together, and they must be replaced together without exception.
The software in the control module can be updated with SPS.
The XWD control module uses information, amongst other things, from the following systems:
- ECM: Requested (accelerator pedal position), current and maximum drive torque, engine speed, activated brake pedal
- YRS: Yaw rate, lateral and longitudinal acceleration
- ESP: Wheel speed of the four wheels
- CIM: Steering wheel angle
- TCM: Current gear
- BCM: Handbrake activated, SPORT mode activated.