Brake lights, detailed description: Notes
The brake lights come on when the brake pedal is depressed. The Rear Electrical Center (REC) monitors the brake light circuits and sends error messages on the bus. The car has brake lights situated in the right and left-hand light clusters as well as a high-level brake light at the top of the rear window. The high-level brake light consists of LEDs.
The brake light lamps in the light clusters are bulb lamps that work together with the parking lights. The brake light lamps in the light clusters are supplied a PWM voltage. When the parking lights are lit, the lamps are supplied a 22 % PWM voltage, which corresponds to the light strength of a 5 W bulb. When the brake lights are lit, B+, PWM 100 %, is supplied to the lamps, which light at full strength. In the event of filament breakage in a bulb normally used as a brake light, the brake light function is taken over by the parking light lamp and a message is displayed in SID.