Brake Lamp: Description and Operation

GF82.10-P-3010R Stop Lamp Actuation, Function

Component Identification:

Stop lamp function

Function requirements:
^ Circuit 15 ON

Function
By engaging the service brake voltage is applied over the switching contacts in the stop lamp switch (S9/1) to the SBC control unit (A7/3n1), which then sends the "stop lamp On" signal over the Controller Area Network bus Sensotronic Brake Control (CAN-SBC) to the ESP, SPS [PML] and BAS control unit (N47-5). The ESP, SPS and BAS control unit (N47-5) relays the signal to the EIS control unit (N73) over CAN-C (CAN-C). From the EIS control unit (N73), the signal is forwarded over CAN-B (CAN-B) to the rear SAM control unit (N10/8).
Parallel to this the SBC control unit (A7/3n1) forwards the "stop lamp On" signal (circuit 54) over a discrete line to the rear SAM control unit (N10/8).

The rear SAM control unit (N10/8) actuates the left stop lamp, taillamp and parking lamp (E3e9) in the left taillamp and the right stop lamp, taillamp and parking lamp (E4e9) in the right taillamp as well as the center high-mounted stop lamp (E21). The signal, which is forwarded parallel to the CAN-signal over a discrete line, is intended to counteract any time-delayed relay of the stop lamp signal over the three CAN data buses.
The stop light signal, in addition to its actual task, i.e. the actuation of the left stop lamp, taillamp and parking lamp (E3e9), the right stop lamp, taillamp and parking lamp (E4e9) and the center high-mounted stop lamp (E21), also has significance for other function areas in the vehicle. For this reason the stop light signal is sent from the EIS [EZS] control unit (N73) to CAN-B (CAN-B) and CAN-C (CAN-C).

The left stop lamp, taillamp and parking lamp (E3e9) and the right stop lamp, taillamp and parking lamp (E4e9) as well as the center high-mounted stop lamp (E21) are designed as light emitting diode (LED) light sources.

Stop lamp flashing on and off function (emergency stop signal as from 11.7.05)

Function requirements
^ Brake actuated
^ Speed > 50 km/h
^ Brake Assist System active or vehicle deceleration > 7.5 m/s2

Function
For optimization of the rear signal representation, in the event of emergency braking the left stop lamp, taillamp and parking lamp (E3e9) and the right stop lamp, taillamp and parking lamp (E4e9) as well as the center high-mounted stop lamp (E21) are actuated to flash on and off.

To this end all the data from the ESP, SPS [PML] and BAS control unit (N47-5) is recorded, generated and issued as an emergency braking signal to CAN-C (CAN-C).
The signal is sent from the central gateway control unit (N93) over CAN-B (CAN-B) to the rear SAM control unit (N10/8).

The rear SAM control unit (N10/8) actuates the left stop lamp, taillamp and parking lamp (E3e9) and the right stop lamp, taillamp and parking lamp (E4e9) as well as the center high-mounted stop lamp (E21) for at least 1 s with a flashing frequency of 5 Hz. If the vehicle comes to a standstill following such a brake application the stop lamp flashing on and off function is reset. Following this the stop lamp function is continuously actuated again.

Reset function
^ Brake not actuated
^ Speed <10 km/h
^ Brake Assist System not active and vehicle deceleration for at least 150 ms < 6.5 m/s2

The stop lamp flashing on and off function is used for all vehicles with EC model homologation.