Design

Design

Control module




The differential electronic module (DEM) is mounted directly on the clutch unit housing. The control module and pump are calibrated together at the factory, but can still be replaced separately due to auto calibration. With auto calibration (done at the workshop via a command when replacing control module or pump), a sequence is run and the results of the sequence give different values from the pump to the differential electronic module (DEM).
Via the CAN, the differential electronic module (DEM) receives signals from:
- Engine control module (ECM)
- Central electronic module (CEM)
- Brake control module (BCM)
- driver information module (DIM).
Conducted by these signals, the Differential Electronic Module (DEM) determines how high the oil pressure to the clutch unit should be. The oil pressure to the clutch driven plates is decisive for how much torque can be transferred to the rear wheels.
In case of Differential electronic module (DEM) failure, four-wheel drive may be reduced or lost completely.

Electrical feed pump.




The electric feed pump is located on the clutch unit and is supplied with voltage from the Differential electronic module (DEM).
The pump starts when the ignition is on and can give a maximum oil pressure of 40 bar. The pump then runs according to the driving situation, where the pressure (engine speed) is decided. At each requested pressure, the differential electronic module (DEM) calculates how the pump should run. The pump consists of an annular piston pump with an integrated regulator. The regulator works under conditions of equilibrium between the oil pressure and the centrifugal force from the regulators.
Four-wheel drive does not function in the event of a fault in the feed pump.
The feed pump can be diagnosed.