Electric Parking Brake Switch: Description and Operation

Electric Parking Brake Inputs and Outputs







Electric Parking Brake Control Unit (located right C-pillar)
- Speed signal - wheel speeds are detected in order to run the various functions, depending on vehicle speed.
- Longitudinal acceleration - the gradient is detected in order to activate/deactivate the Drive-Off Assistant.
- Output signals to the PSM hydraulic unit - targeted buildup of brake pressure during emergency braking

Parking Brake Switch







Press = apply, pull = release, press continuously = initiate
emergency braking function

Brake Light Sensor







Instead of a conventional brake light switch, a Hall sensor transmits the position of the brake pedal. The sensor can be adjusted by moving it in the holder.

Clutch Sensor







The clutch sensor is installed on the clutch master cylinder in order to record the position of the master piston. The piston contains a permanent magnet for this purpose. The different positions of the magnet generate certain field strengths, which can be used to determine the sensor position. The sensor supplies up to three different signals, which provide information about the position of the piston. Clutch pedal actuated, piston travel and clutch pressed.

- The first signal switches off adaptive cruise control.
- The next signal is a PWM signal, which indicates the piston travel. This is used in conjunction with the Drive-Off Assistant to slowly reduce the brake pressure, depending on clutch travel.
- The third signal, with the clutch pedal fully depressed, is the switching position for the Start Lock function Interlock).

Emergency release function of the electric parking brake







Emergency release procedure using the actuator:
1-Loosen the oval-head screw on the back of the actuator using an Allen key (a/f 3).
2-Access the emergency release screw using an Allen key (a/f/3).
3-Complete approx. 300 turns anti-clockwise with a torque of less than 100 Nm (74 ft lb.). Keep turning until the torque increases perceptibly. The fully released position of the brake shoes is then reached.