Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Electronic function
- Oil pressure and temperature sensor
- Differential electronic module (DEM)
- Control valve/axial solenoid
- Electrical feed pump.
The differential electronic module (DEM) is secured directly to the coupling unit and forms a single unit with the axial solenoid and control valve. The differential electronic module (DEM) receives signals from the engine control module (ECM) and the brake control module (BCM) via the control area network (CAN). The differential electronic module (DEM) uses the sensor signals to control the oil pressure to the multi-plate clutch by adjusting the axial solenoid. The axial solenoid regulates the control valve constantly using a pulse width modulation (PWM) signal. The oil pressure for the multi-plate clutch determines the amount of torque which can be transferred to the rear wheels.
If the car has dynamic stability and traction control (DSTC), the required stability control is applied before four wheel drive.
Active On demand Coupling (AOC) has an oil pressure and temperature sensor, which gauge the prevailing temperature and pressure of the hydraulic fluid. The oil pressure and temperature sensor provide the differential electronic module (DEM) with information about the temperature and pressure. Four wheel drive is disengaged to protect the coupling unit from damage if the temperature becomes too high, above 97 °C. The coupling unit is re-engaged at full function when the temperature falls below 93 °C.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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