Audi Workshop Service and Repair Manuals

Control unit for ABS with EDL/TCS/ESP -J104

The control unit is combined with the hydraulic unit to form an assembly group. It controls ESP, ABS, EDL, TCS, EBPD and overrun torque limiting function. A control unit self test is performed on switching on the ignition. All electrical connections are permanently monitored and the solenoid valve function is tested periodically. The normal braking system only is available on total failure of the control unit.

Steering angle sender -G85

The steering angle sender is fitted in a joint housing with the airbag coil connector. It is located on the steering column between steering column switch and steering wheel. It sends the steering angle lock of the steering wheel via the CAN bus to the ABS/TCS/ESP control unit -J104. Zero position compensation must be performed after replacement of the control unit or the sender. The ESP function fails if the sender is defective.

Lateral acceleration sensor -G200

The lateral acceleration sender sends the cornering force values to the ABS/TCS/ESP control unit -J104. The ESP function fails if the sender is defective.

Yaw rate sender -G202

The yaw rate sender records data, called yaw rates, which attempt to rotate the vehicle about its vertical axis and sends them to the ABS/TCS/ESP control unit -J104. The ESP function fails if the sender is defective.

Brake pressure sender -G201

The brake pressure sender records the current brake pressure in the brake circuit and sends it to control unit -J104. The control unit uses this to calculate the wheel brake forces and the longitudinal forces acting on the vehicle. The ESP function fails if the sender fails.

Switch for TCS/ESP E256

The switch enables the driver to switch off the ESP function. Pressing the brake pedal or pressing the switch again switches it back on. If it has not been switched on again, the system reactivates itself automatically when the engine is next switched on. The system cannot be switched off during a current ESP operation and after a certain speed has been reached.

Switch for brake recognition -F83

The brake recognition switch is also known as a release switch and operates like a two-way switch When the driver brakes, the switch changes from signal contact 1 to signal contact 2. Since there is always only one signal contact closed, the system can clearly identify the current status, thus the release switch provides a high degree of intrinsic safety.

ESP hydraulic pump V156

To generate the necessary admission pressure on the suction side of the return pump, a hydraulic pump is also required. The pre-charge pressure is limited by a restrictor in the main cylinder, hydraulic pump V156 itself is not regulated.