Electronic Differential

WARNING: This page is about a different car, the 2011 Jaguar XKR, 2011 Jaguar XK, 2010 Jaguar XKR, and 2010 Jaguar XK. However, it is still accessible from the selected car via links, so may be relevant.

The multi-plate clutch prevents excessive differential slip and therefore maximizes the traction performance of the vehicle. This is fundamentally different from 'braked' traction control systems, which can only counteract differential slip when it occurs.

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). The ADCM monitors the driver's demands through 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 multi-plate clutch actively controls the torque flow through the differential and optimizes the torque distribution in the driveline. The clutch biases the torque from the differential to the wheel with the higher grip and prevents the wheel with the lower grip from spinning.

The differential strategy in the ADCM includes:

A pre-loading function, increasing locking torque with increased driving torque.
A slip controller to decrease locking torque for optimum comfort, e.g. parking.

The ADCM memorizes the position of the motor when the ignition is switched off.

controller area network (CAN) bus messages used by the ADCM include wheel speed, steering angle, automatic transmission speed, temperature information, car configuration, axle ratios and mode inputs.

The ADCM also sends messages via the controller area network (CAN) bus to tell other control modules on the network the status of the electronic differential. The clutch torque and default mode status are some of the main signals sent out by the ADCM.

If the DLM or ADCM are replaced, a Jaguar approved diagnostic system must be connected to the vehicle and the differential self-calibration procedure must be performed. This procedure must also be performed if the motor or electronic differential is replaced.

If a fault occurs with the electronic differential, the ADCM, the DLM, or one of the required input signals, the ADCM records an error code and displays a warning in the message center.

The following messages can be displayed:

Message	Description	Chime
EDIFF NOT AVAILABLE	Differential temperature has reached the overheat threshold. System deactivated until temperature returns within limits.	Single
EDIFF SYSTEM FAULT	Fault has occurred with electronic differential. System deactivated until fault rectified.	Single