Brake light switch

Two switches are fitted in the brake light switch: the brake light switch and the brake light test switch (redundant for safety reasons). The signals enable the DME control unit to determine whether or not the brake pedal is depressed.

Fig 1: Identifying Brake Light Switch And 4-Pin Plug Connection

Courtesy of BMW OF NORTH AMERICA, INC.

BRAKE LIGHT SWITCH PARTS DESCRIPTION

Item	Explanation
1	Brake light switch
2	4-pin plug connection

The brake light switch is supplied with 12 Volts, terminal R and earth. Two signal lines lead into the DME. When the brake pedal is not pressed, the brake light switch delivers 0 Volts and when the brake pedal is pressed it delivers 12 Volts via the signal line to the DME. The brake light test switch delivers the same signals to the DME.