Electronic Function

Fig 1: Identifying Differential Electronic Module (DEM) Components

Courtesy of VOLVO CARS OF NORTH AMERICA.

1. Control module for all wheel drive (differential electronic module)
2. Stepper motor
3. Control valve
4. Pressure flow
5. Control valve cover

The differential electronic module is mounted directly onto the housing for the coupling unit. It forms part of a unit with the stepper motor and the control valve. The differential electronic module communicates with the engine control module (ECM) and brake control module via the control area network (CAN). The differential electronic module uses the sensor signals to control the oil pressure on the multi-plate clutch by adjusting the control valve. The oil pressure on the multi-plate clutch determines the torque that can be transferred to the rear wheels.

The Active On Demand Coupling has a temperature sensor. This measures the temperature of the hydraulic fluid and transmits it to the differential electronic module. All wheel drive is disengaged if the temperature is too high. This prevents damage to the coupling unit.