Trailer lighting

The trailer lighting runs the following functions:

• Brake light
  
• Sidelights
  
• Flashing
  
• Hazard warning lights
  
• Rear fog light
  
• Reversing light
  

Brief description of components

Light module

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

If the processor fails, there is no communication with the trailer module.

Trailer module

The trailer module is an auxiliary module to the light module.

The trailer module

• disconnects the load power circuit of the trailer from the current circuits of the towing vehicle and
  
• monitors the lights of the trailer.
  

The trailer module is fitted if the vehicle is equipped with a trailer hitch.

The trailer module detects a trailer as hitched when at least two loads are detected at the lamp outputs. The trailer module reports the ”status trailer” via the K-CAN SYSTEM to the light module. This signal is required by a number of systems of the towing vehicle: on the towing vehicle, a number of functions are switched off when a trailer has been detected:

• The rear fog light of the towing vehicle is switched off to avoid dazzling the driver with reflections.
  
• The reversing lights of the towing vehicle are switched off to avoid dazzling the driver with reflections.
  
• The rear PDC (park distance control) is switched off when a trailer has been detected.
  

The trailer module consists of

• a microcontroller and
  
• overload-resistant power switches for the trailer power circuits. The microcontroller of the trailer module activates the power switches.
  

The trailer module receives input signals from the light module

• via the K-CAN SYSTEM data bus and
  
• via a hard-wired cable from the right-hand brake light of the towing vehicle. If the K-CAN SYSTEM or the microprocessor fail, this input activates the following functions: taillights and brake light function.
  

The trailer module activates

• the brake lights
  
• the left and right turn indicator lamps
  
• the left and right licence plate lights
  
• the left and right sidelights.
  

Signal path: light module -> trailer module.

Rear fog light

Switching on the rear fog light:the rear fog light of the trailer is switched on when with

• Terminal 15 On and
  
• light switch in position low beam
  
• the rear fog light button is pressed.
  

Orwhen

• Terminal 15 On and
  
• light switch in position sidelights and
  
• the fog light button is pressed again and
  
• the rear fog light button is pressed.
  

Switching off the rear fog light: the rear fog light is switched off again when

• the rear fog light button is pressed again.
  
• terminal 15 OFF,
  
• light switch OFF.
  

Reversing light

The reversing lights are switched on when

• Terminal 15 On and
  
• reverse gear is engaged.
  

The reversing lights are switched on with a delay of a fraction of a second to avoid flashing during gear changes.

Main functions

Flashing

For turn indicators, there are two indicator functions:

• One-touch indicating: If the turn indicator-low beam switch is touched briefly, the turn indicator lamps are activated briefly (as often as coded). One-touch indicating can be used, for example, when changing lanes.
  
• Continuous flashing: If the turn indicator-low beam switch is ”pressed beyond” the pressure point, the turn indicator lamps are activated with the function ”continuous flashing”. Continuous flashing is the turn indicator function, e.g. before turning right or left.
  

If one of the turn signal indicator lamps on the vehicles or on the trailer is defective, the flash rate is doubled.

Hazard warning lights, crash alarm hazard warning lights, DWA alarm hazard warning lights

The three triggers for hazard warning lights on the trailer are:

• Hazard warning lights switched on by the driver using the hazard warning lights button: the trailer also flashes.
  
• Crash alarm hazard warning lights (the hazard warning lights button also flashes). If the ISIS (Intelligent Safety Integration System) detects a crash, the hazard warning lights are switched on (dependent on the coding). The hazard warning lights can be switched off again using the hazard warning lights button. The trailer also flashes in the case of crash alarm hazard warning lights.
  
• DWA alarm hazard warning lights: the hazard warning lights button does not flash. The trailer also flashes in the case of DWA alarm hazard warning lights. However, the trailer does not issue acknowledgement flashing on activating/arming the DWA.