Ford Kuga

 Service Manual

Rear Drive Axle/Differential » Rear Drive Axle and Differential (System Operation and Component Description)
All-wheel drive control unit

The all-wheel drive control unit is bolted directly to the housing of the Haldex clutch.

It forms one unit made up of the control valve, a pressure/temperature sensor, and a control module. It receives signals from the PCM and from the ABS control module via the CAN data bus. The control module in the control unit uses these signals to determine the fluid pressure that is needed to actuate the clutch plates depending on the requirement. This determines how much torque should be transmitted to the rear wheels. All-wheel drive is deactivated if a fault occurs in the all-wheel drive control unit.

A preload of approx. 80 Nm is always present at the Haldex clutch.

The temperature sensor of the Haldex clutch is installed near the control valve in the control unit and is surrounded by the hydraulic fluid. The temperature is transmitted to the control module and is used for adaptation to the changing viscosity of the hydraulic fluid. If the hydraulic fluid is cold, the control valve has to be opened slightly more than requested. This allowance has to be reduced as the temperature increases. The normal working temperature of the hydraulic fluid is between +40 C and +60 C. If the temperature rises above 100 C, the clutch is depressurised; if the temperature falls below 95 C, the clutch is pressurised again.

All-wheel drive is deactivated and a diagnostic trouble code set if a fault occurs in the temperature sensor.

With Haldex Generations I and II, the control valve was actuated via a stepper motor. With Haldex Generation III, the stepper motor has been omitted.

The control valve is now actuated via a solenoid valve. The solenoid valve is actuated by the control module in the all-wheel drive control unit by means of pulse width modulation. The pulse width modulation determines the position of the adjustment spindle and thus the opening cross section of the return hole. This is how the pressure at the working piston of the plates is determined.

If the return hole is fully closed, maximum pressure is applied to the plates. If the return hole is fully open, the plates are unpressurized.

General Information

Driving situations

Haldex clutch

Design of the 3rd generation Haldex clutch

Design of the multi-plate clutch

All-wheel drive control unit

Electric feed pump

Pressure control - 3rd generation Haldex clutch

Base pressure

Increased base pressure (preload)

Pressure build-up

Design of the 4th generation Haldex clutch

Pressure control - 4th generation Haldex clutch