Brake light

The brake light functions in 2 stages: normal braking and strong braking. In the case of strong braking, the side lights / brake light lamps are also activated (dependent on coding and country variant).

Brief description of components

Brake light switch

The brake light switch is an electronic switch. The brake light switch is supplied with power by the light module as of terminal R ON.

For safety reasons, the brake light switch contains 2 switch outputs:

• One output is connected with the light module.
  
• One output is connected to the CAS (Car Access System) control module. The CAS evaluates the brake signal and passes it on to the K-CAN SYSTEM data bus.
  

The signal ”brake light switch operated” is thus received by two independent control modules and passed on. If one of the two signal paths fails, the other still functions.

Light module

The light module controls and monitors the vehicle lights. Information is received and sent via the data bus K-CAN SYSTEM.

The faults of the xenon headlights are evaluated in the light module.

Emergency operation properties of the light module: The light module is supplied with terminal 30 twice.

If a terminal 30 fails, the following are activated:

• Front lighting: low beam and parking light (each on one side).
  
• Tail lighting: On one side, the outer side lights/brake lights are activated (parking light). On the other side, the inner taillights are activated. The vehicle thus still has lights on both sides. Confusion with a one-track vehicle (motorcycle) is excluded.
  
• Brake light: One side of the brake lights is activated with normal power (ECE coding).
  

In the case of a failure of the processor, emergency operating mode is activated. Emergency operating mode involves hardware that is completely independent of the light module. Emergency operation properties with failure of the processor:

• Vehicle lighting: At terminal 15 On, the following are switched on: Front low beam and rear side lights / brake light lamps left and right. The side lights / brake light lamps left and right are not, as would be normal, dimmed to 10% of their brightness, but operated with full power. This ensures the function of the vehicle lighting irrespective of the position of the light switch.
  
• Brake light: With terminal 15 On, the left and right brake lights are switched on when the brake light switch is operated (via a hard-wired, direct line from the brake light switch to the lamp drivers).
  

Function defects with failure of the processor:

• No turn indicators and hazard warning lights, no high beam, no headlight flasher, no rear fog light, no third brake light
  
• No communication across the K-CAN SYSTEM.
  

Brake lights

The brake lights are light emitting diodes (LEDs). The LEDs are not monitored by the light module.

Additional (center) brake light

The center brake light consists of light emitting diodes (LEDs). The LEDs are not monitored by the light module.

Side lights / brake light lamp

Side light/parking light (taillight) and brake light can be combined on the left and right into one light. This light consists of light emitting diodes (LEDs). The LEDs light up in two different brightnesses, depending on function:

• Side light/parking light: the light emitting diodes are activated with 10% of their power.
  
• Braking stage 2 (dependent on coding): in the case of strong braking, the LEDs are activated at 100% power.
  

The LEDs are not monitored by the light module.

Main functions

Normal braking: braking stage 1 (EC coding)

In the case of simple braking, the

• brake lights on the left and right and the
  
• center brake light go on.
  

Strong braking: braking stage 2 (EC coding)

In the case of strong braking, in addition to the brake lights on the left and right and center, the side lights/brake light lamps are also activated:

Braking stage 2 is activated

• when strong deceleration is detected or
  
• when an ABS intervention takes place (anti-lock braking system activated).
  

Country-specific version

USA

In the USA country variant, the two stages of the brake light are coded as follows:

• Braking stage 1: brake light and side lights / brake light lamp
  
• Braking stage 2: brake light, side lights / brake light lamp, and additionally brake lights
  

If a terminal 30 of the light module fails, the following are activated:

• brake light on one side of the vehicle
  
• side lights / brake light lamp on the other side of the vehicle