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System Description
EDL
Electronic differential lock
The electronic differential lock (EDL) is an aid when driving away from a standstill. An electronically controlled brake application on the spinning driven wheel provides a torque reaction point for the differential. This enables the wheel with better traction to make use of the engine power. This also applies when reversing.
EDL is standard equipment on vehicles with 4WD. While EDL acts on all four wheels in vehicle with 4WD on vehicles with FWD it acts only on the front wheels. A mechanical differential lock is not required.
The EDL control function can be initiated at road speeds up to 40 km/h. Once EDL has been activated it cuts out automatically at a predetermined upper speed threshold of 40 km/h on vehicles with FWD and 80 km/h on vehicles with four wheel drive.
Suction dampers are fitted in the hydraulic unit. They assist the build-up of pressure in the corresponding wheel brake cylinders when EDL is active. The operating range of the pressure limiting valve in the hydraulic unit is 170 ± 25 bar.
To stop the brakes overheating the EDL control function is suppressed if the temperature of the brakes exceeds a certain value. The temperature value is defined in control unit-J104. The temperature of the brakes is calculated by the control unit using a simulation formula. The EDL is then reactivated if the calculated temperature drops below a predetermined lower threshold. The operation of the brake system and the ABS function are not affected by this automatic cut-off feature.
When the ignition is switched off, the calculated temperature of the hot brakes is stored in the memory until the ignition is switched on again. When the ignition is switched on, the dash panel insert sends a time signal which enables the control unit -J104 to calculate the period the vehicle has been left standing. This period is put into the temperature simulation formula to calculate the new temperature of the brakes. If the vehicle has been left standing for more than one hour, the control unit will automatically assume a brake temperature equal to the lowest value in the simulation formula.
If EDL is switched off due to temperature limit being exceeded this is indicated in measured value block for a period of 20 ignition cycles.
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