Part I
LED Headlight
LED headlight
The LED headlights are used for exterior lighting.The vehicle equipment with LED headlights serves to ensure identification of the vehicle and illumination of the driving area.The LED headlights therefore contribute to active road safety.
LEDs are construction components made from semiconductors.In the LED, the energy from the electrical current is converted into light energy.As the individual LEDs emit a smaller quantity of light than incandescent bulbs or xenon bulbs, several LEDs are usually bundled and interconnected in so-called LED modules.
The advantages of LEDs are:
- Long service life
- High efficiency
- Mechanical robustness
- Adaptation of light colour
- Option of dimming
The vehicle equipment with LED headlights includes the following lighting functions:
- Parking lamps
- Parking lamps
- Daytime running lights
- Driving light
- High-beam headlight and headlight flasher
- Turn indicator, front
- Hazard-warning flashers
- Cornering light
The following different LED headlights are available:
- LED headlight for right-hand traffic
- LED headlight for left-hand traffic
- US version
Depending on the national-market version, the lighting functions for vehicles with LED headlights additionally include cornering light and high-beam assistant.
The following graphic shows the control units with functionality related to the LED headlights.
Brief component description
The following components for controlling the LED headlights are described:
- LED headlight
- LED main light module
- Headlight driver module
- LED module, cornering light
- Car Access System
- Junction Box Electronics
- Footwell module
- Central gateway module
- Integrated chassis management
- Crash safety module
- Controller
- Steering column switch cluster
- Roof function centre
- Rain-light-solar-condensation sensor
- Camera-based driver support systems
- Operating facility for light
- Turn signal/high beam switch
- Hazard warning flasher switch
LED headlight
The LED headlights are fitted above the front bumper panel.The following lighting functions are performed by the LED headlights:
- Parking lamps
- Parking lamps
- Daytime running lights
- Low-beam headlights
- High-beam headlamps
- Turn indicator, front
- Hazard-warning flashers
- Cornering light
A different number of LEDs fitted on corresponding LED supports are responsible for each of the lighting functions.
Lighting function Light source for each LED headlight
Positioning light and side 1 LED support with 2 LEDs
marker lights
Lighting ring for side lights 2 LED supports, each with 4 LEDs
and daytime driving lights
Low-beam headlights 2 LED supports, each with 10 LEDs
High-beam headlamps 2 LED supports, each with 5 LEDs
Turn signals 1 LED support with 8 LEDs
Cornering light 1 LED support with 5 LEDs
Therefore, 25 LEDs provide the driving light for each LED headlight.When the high-beam headlight is activated, 10 further LEDs on 2 LED supports are switched on for the high-beam function of an LED headlight.
The following graphic shows the front components of the exterior lights that are visible from the outside.
The following graphic shows various views of the right LED headlight.
LED main light module
The LED main light module is fitted on the underside of the LED headlight.
The LED main light module controls the following functions:
- Low-beam headlights
- High-beam headlamps
- Headlamp flasher
The lighting functions are controlled via terminals 56 a and 56 b.
The LED main light module also regulates the temperature control in the LED headlight.The values of 3 temperature sensors and the signals relating to driving speed and ambient temperature communicated via the LIN bus serve as an input signal.The fans are regulated differently.After switching off the lighting function, an after-run of the fans of up to 60 seconds is possible.The temperature control also includes a function for de-icing the LED headlight.
In the event of a temperature sensor failure, the fans are switched on full blast to protect the components in the LED headlight.For diagnosis of the fans and temperature sensors, the data from the LED main light module is transferred to the footwell module (FRM) via the LIN bus.
Headlight driver module
The headlight driver module is fitted as a printed circuit board in the LED headlight.The headlight driver module evaluates the signals sent from the footwell module (FRM) via the LIN bus.In this process, the headlight driver module assumes control of the following lighting functions of the LED headlight:
- Parking lamps
- Daytime running lights
- Side marker light
- Turn signals
- Positioning light
Besides the lighting functions, the headlight driver module also controls the stepper motors of the headlight beam throw adjustment and of the cornering light.
LED module, cornering light
The LED module cornering light is fitted in the LED headlight as an additional light source.Country-specific settings are possible using encoding.In the Korean national-market version, the cornering light is not available for example.
The modular design enables the cornering light LED module to be changed in the existing LED headlight.
Car Access System
The Car Access System (CAS) is the control unit that regulates access to the vehicle (key identification).It checks the prerequisites for release before the junction box electronics (JBE) and the footwell module (FRM) are controlled.The Car Access System (CAS) is directly connected to the K-CAN2.The Car Access System (CAS) prepares signals and makes these available to other bus users in the vehicle electrical system.
Junction Box Electronics
The junction box electronics (JBE) module combines many functions that are made available to the other bus users.
The junction box electronics (JBE) module requests the status of the ambient brightness from the rain-light-solar-condensation sensor via the LIN bus.The Junction Box Electronics (JBE) module transmits the status via K CAN2. The footwell module (FRM) assesses the status of the ambient brightness.
Footwell module
All functions of the exterior lights are controlled by the footwell module (FRM).
The footwell module (FRM) receives many input signals that lead to the switching on of the LED headlight.The footwell module (FRM) forms the interface to the instrument cluster (KOMBI).It enables communication between the LIN bus and the K-CAN and therefore message transmission to the respective other data bus.
Central gateway module
The central gateway module (ZGM) links all of the data buses.The central gateway module's (ZGM) gateway function enables data exchanges amongst the various bus systems.Stored system functions can be called up using appropriate commands.
Integrated chassis management
Data from ride height sensors at the front and rear axle is evaluated directly by the Integrated Chassis Management (ICM).The automatic headlight beam throw adjustment thus ensures that oncoming traffic is not dazzled.In addition to the sensors for driving dynamics control, the Integrated Chassis Management (ICM) includes a longitudinal and a lateral acceleration sensor for impact detection.Two wires provide a direct connection between the Integrated Chassis Management (ICM) and the Crash Safety Module (ACSM) for transmission of the sensor signals.The footwell module (FRM) receives signals from the Integrated Chassis Management (ICM) through the K-CAN2.Within the central gateway module (ZGM) the FlexRay transfers the signal to K CAN2.
Crash safety module
The Crash Safety Module (ACSM) is the control unit for the passive safety system.
It evaluates the longitudinal and a lateral accelerations of all sensors concerned.Comprehensive tests were used to define triggering thresholds for all possible types of accident.The Crash Safety Module (ACSM) transmits a message to other bus users when the restraint systems are triggered. Depending on the accident severity to be expected, each of the control units performs certain functions, such as activation of the hazard warning flasher by the footwell module (FRM).
Controller
The controller (CON) is connected to the central information display (CID) via the body CAN. The Central Information Display (CID) serves to display the vehicle functions that can be selected and configured.There are 7 fixed selector keys around the controller (CON).
The following functions of the LED headlights can be set using the controller (CON) in the Central Information Display (CID):
- Daytime running lights
- Duration of headlight courtesy delay feature
- Visual acknowledgement of central locking system
- Welcome lamps
- Brief turn signal activation
Steering column switch cluster
The steering column switch cluster (SZL) features one steering column switch each on the left and right sides.The right-hand steering column switch is designed for operating the functions of the wash/wipe system.The steering column switch on the left side of the steering column controls the high-beam headlight and turn indicators as well as operation of the on-board computer. The signals are made available by the steering column switch cluster (SZL) via the FlexRay.The signals of the integrated steering angle sensor are also transmitted to the Integrated Chassis Management (ICM) via the FlexRay.
To control the LED headlight, the steering column switch cluster (SZL) transmits the following requests to the footwell module (FRM):
- Turn indicator light
- Parking lamps
- High-beam headlamps
- High-beam assistant
- Headlamp flasher
Roof function centre
The roof function centre (FZD) with its integrated ultrasonic interior movement detector provides the signal for the optical alarm via K CAN2. The footwell module (FRM) therefore allows the anti-theft alarm system to provide an visual alarm using the turn indicators.
Depending on vehicle equipment, the roof function centre (FZD) includes:
- Emergency call button with emergency call LED
- Interior lighting
- Slide/tilt sunroof switch.
The following graphic shows the high version of the roof function centre (FZD).
Rain-light-solar-condensation sensor
The rain-light-solar-condensation sensor receives its voltage supply from the roof function centre (FZD) and consists of the following sensors:
- Rain sensor
- Light sensors
- Solar sensor
- Condensation sensor
The 2 light sensors (forward light sensor and ambient light sensor) register ambient brightness and monitor the lighting ahead of the vehicle. The light sensors supply the signal for switching on or off the automatic driving lights control.
Camera-based driver support systems
Depending on the options fitted, various camera-based systems are available. The light points, light colours and light intensities picked up by the video camera are evaluated by the KAFAS control unit. The evaluation by the KAFAS control unit results in a recommendation to switch on or off the high-beam assistant.Technically, the system is implemented with a joint camera and a joint control unit, the KAFAS control unit. The functions of the camera-based driver support systems are:
- Lane departure warning
- High-beam assistant
- Road sign recognition
Operating facility for light
The LED headlights can be switched on and off using the operating facility for lights.The operating facility for lights includes both the light switch and additional components for other lighting functions.
The following table shows from which terminal the LED headlights are switched on.
Turn signal/high beam switch
The turn indicator and the high-beam headlight are operated using the turn signal/high beam switch on the left steering column switch of the steering column switch cluster (SZL).The signal from the turn signal/high beam switch is transmitted both via FlexRay protocol and through a separate line to ensure functional redundancy. The central gateway module (ZGM) transmits the signal to the K-CAN2.This is how the footwell module (FRM) receives the signals from the turn signal/high beam switch.The turn indicator lights continue to operate if the information fails to reach the footwell module (FRM) through the bus system.This redundant data-transmission is also employed for the one-touch flashing and headlight flasher functions.
Hazard warning switch
The hazard warning switch is fitted in the fresh air grille in the centre of the dashboard.The hazard warning switch comprises a single assembly in combination with the central locking button.
The hazard warning flashers are activated by pressing the hazard warning switch. All turn indicators are activated simultaneously and the hazard warning switch also flashes.
If the turn signal/high beam switch is pressed in the direction for left or right turns while the hazard warning flashers are operating, the turn indicator light assumes priority.
The system reverts to operation of the hazard warning flashers after "Terminal 15 off" or when the turn indicator light has returned to its original position.If the hazard warning switch is depressed while the turn indicator lights are operating, then the hazard warning flashers assume priority.
With "Terminal 30 on" the hazard warning flashers are implemented in their energy-saving mode. In this mode, the hazard warning flashers light up for a shorter period and remain off for a longer period than usual.
When the anti-theft alarm system is signalling an active alarm the hazard warning switch is suppressed and does not flash with the alarm system.
System overview
System functions
The following lighting functions of the LED headlights are integrated in the footwell module (FRM):
- Parking lamps
- Daytime running lights
- Driving light
- High-beam headlight
- Headlamp flasher
- Adaptive Headlights
- Turn indicator
- Hazard-warning flashers
- Parking lamps
- Welcome lamps
- "Follow-me-home" lighting
The LED headlights are supplied with voltage via the footwell module (FRM).The LED main light module receives the information used to control the voltage supply to the LEDs from the footwell module (FRM) through the LIN bus.
In addition to the lighting functions listed, other exterior lights functions are also integrated in the footwell module (FRM):
- Automatic headlamp control
- Variable light distribution (European market version)
- Automatic headlight beam throw adjustment
- Light monitoring
- Cold monitoring at "lights off"
- Hot monitoring at "lights on"
- Optical alarm and optical feedback signal
- Central locking system
- Anti-theft alarm system
- Crash signal present
- Emergency lighting with "Terminal 15 off"
- Emergency light operation
- High-beam headlamps
The following system functions are described:
- Parking lamps
- Welcome lamps
- Daytime running lights
- Driving lights and high-beam headlights
- High-beam assistant
- Automatic headlamp control
- Adaptive Headlights
- "Follow-me-home" lighting
- Cornering light
- Variable light distribution
- Automatic headlight beam throw adjustment
- Turn signals
- Hazard-warning flashers
- Parking lamps
- Visual feedback signal from central locking system
- Emergency light operation
Side lights
To make the parked vehicle easier to identify in darkness, the light switch of the operating facility for lights must be turned to "Position 1".To activate the side lights, the 2 lighting rings and the positioning lights are supplied with pulse-width-modulated voltage.
When the side lights are operating, an acoustic signal sounds if the driver's door is opened, while a Check Control message also appears in the instrument panel's display panel. Leaving the side lights on can drain the vehicle's battery.
When the side lights are switched on, the following lights are also activated:
- Positioning light
- Lighting rings of the side lights
- Side marker light
- Indicator lights in the instrument cluster (KOMBI)
Welcome lights
When the vehicle is unlocked the side lights are switched on for approximately 20 seconds. This makes it easier to determine the vehicle's precise location under low-visibility lighting conditions.
Before the welcome lights can be activated the light switch must first be turned to "Position 2" or "Position A".The welcome lights are activated as soon as the vehicle's locks are disengaged. The Car Access System (CAS) provides the central locking signal through the K-CAN2.The footwell module (FRM) receives an "unlock" signal and switches the welcome lights on. When the welcome lights are switched on, the following lights are also activated:
- Interior lighting
- Positioning light
- Lighting rings
- Side marker light
- Indicator lights in the instrument cluster (KOMBI)
Daytime driving lights
The daytime driving lights are realized by the positioning lights and the lighting rings in the LED headlight.However, the pulse width modulation is cancelled and the LEDs are supplied directly with full voltage from the vehicle voltage.This makes the daytime driving lights substantially brighter than the side lights.
The light switch must be turned to "Position 0" before the daytime driving lights can be activated. The daytime driving lights can also be activated by the automatic driving lights control when the rain-light-solar-condensation sensor indicates high-intensity ambient brightness. The light switch must be in its "Position A".
On national-market versions with this feature, the daytime driving lights are activated when terminal 15 is switched on.Via "Personal Profile" in the Central Information Display (CID), the daytime driving lights can be activated or deactivated using the controller (CON).The daytime driving lights are switched off at "Terminal 15 off".
In the following national-market versions it is not possible to deactivate the daytime driving lights using the "Personal Profile" feature (encoded element):
- Canadian market version
- Russian market version
- Japanese national-market version
Driving lights and high-beam headlights
The light switch of the operating facility must be rotated to "Position 2" to activate the driving light. When the driving lights are switched on, the LEDs of the low-beam function for the LED headlight are switched on in addition to the LEDs of the side lights.When the engine is switched off the side lights remain on, even if the light switch remains in "Position 2".When the driver's door is opened, the side lights are also switched off.
Pressing the turn signal/high beam switch manually activates the high-beam headlight.
In "Position A", the driving lights are switched on or off according to the lighting conditions by the footwell module (FRM) via the rain-light-solar-condensation sensor.
The LED headlight executes a reference run each time the voltage supply to "Terminal 15" is activated.This process initializes the movement ranges of the automatic headlight beam throw adjustment and the adaptive headlights.
The high-beam headlight is switched on under the following preconditions:
- "Terminal 15 on"
- Driving light on
- High-beam headlight selected at turn signal/high beam switch or with high-beam assistant activated
A blue indicator light in the instrument cluster (KOMBI) shows that the high-beam headlight is activated.
The headlight flasher is activated by pulling back the turn signal/high beam switch.
High-beam assistant
The light switch of the operating facility for lights must be rotated to "Position A" to activate the high-beam assistant.When the driving lights are switched on, the activated high-beam assistant transmits a recommendation to switch on or off the high-beam headlight at the footwell module (FRM).The high-beam assistant takes into account lights on approaching and preceding traffic as well as sufficient ambient brightness.The high-beam assistant ensures that the high-beam headlights are activated whenever traffic situations allow.
The high-beam headlight can always be switched on and off through manual intervention.To activate the high-beam assistant, the high-beam assistant button on the turn signal/high beam switch must be operated.
Manual high-beam activation and dipping
- Switch on high-beam headlight by pushing the turn signal/high beam switch
- Switch off high-beam headlight by pulling the turn signal/high beam switch
To reactivate the high-beam assistant, operate the high-beam assistant button on the turn signal/high beam switch again.
The indicators in the instrument cluster (KOMBI) are as follows:
- High-beam indicator light (blue)
- High-beam assistant indicator lights (green)
- Check Control symbol for failure of the high-beam assistant (yellow)
Limits of the system
The high-beam assistant cannot serve as a substitute for the driver's own judgement regarding use of the high-beam headlights.Thus the headlights must be dipped manually whenever conditions render it necessary to do so. Operation of the high-beam assistant is restricted, or it may fail to operate entirely, under the following conditions:
- Unfavourable weather conditions such as fog or heavy precipitation
- Low visibility road user
- Sharp curves, steep rises and dips
- Crossing traffic or partially hidden traffic on dual carriage ways
- Poorly lit towns and intense reflections from road signs
- Low driving speed
- Windscreen dirty in the area in front of the rain-light-solar-condensation sensor
- Windscreen dirty in the area in front of the camera
The field of view of the light sensors and the camera is on the front of the inside mirror.Do not cover the area in front of the inside mirror with stickers or vehicle tax discs.
The high-beam assistant is not available in the Japanese national-market version.
Automatic driving lights control
The following preconditions must be satisfied before the driving light can be activated automatically:
- Light switch in "Position A"
- "Terminal 15 on"
- Rain-light-solar-condensation sensor reports insufficient ambient brightness.
The LIN bus provides the link between the rain-light-solar-condensation sensor and the Junction Box Electronics (JBE) module. The junction box electronics (JBE) transmit a signal to the footwell module (FRM) via the K-CAN2.If conditions call for activation or deactivation of the driving light, the process is executed by the footwell module (FRM). The automatic driving lights control switches on the driving light together with the side lights. Should no signal be received from the rain-light-solar-condensation sensor owing to a fault while the automatic driving lights control is activated, the footwell module (FRM) will respond by switching on the driving lights.Once the headlamps have been switched on by the automatic driving lights control, they can be switched off again with the light switch of the operating facility for lights or by the rain-light-solar-condensation sensor, provided the ambient brightness is adequate.
Even after "Terminal 15 off" the side lights can remain on because they were activated by the automatic driving lights control system.The side lights are switched off automatically when the driver's door is opened. When the occupants exit the vehicle from another door, the side lights are switched off when the vehicle's locks are engaged.
The footwell module (FRM) will only switch on the driving lights when there is low ambient brightness.There may thus be a delayed activation of the driving lights when the vehicle enters a tunnel or a tree-shaded lane.The light switch of the operating facility for lights must be in "Position A".