Brake light switch

Together with the signal from the brake pressure sensor, braking operations are detected. Two switches (2-stage) are installed in the brake lamp switch. A signal is then made available to the DSC across a line. The engine control unit receives both signals. The engine control unit sends the signal on the PT-CAN. The DSC control unit uses both signals to detect whether the brake pedal has been pressed.

Fig 1: Identifying Brake Light Switch

Courtesy of BMW OF NORTH AMERICA, INC.

The Car Access System (CAS) supplies the brake-light switch with terminal R.