The Body Control Unit is installed in the relay box (left plenum chamber)
There are 3 Body Control Module variants:
- Body Control Multitimer
- Body Control Multitimer and central locking
- Body Control Multitimer, central locking and anti-theft alarm system
The Body Control Module has diagnostic capability. After being replaced the Body Control Module software must be adapted to the vehicle configuration, e.g. the daytime driving light function can be adjusted.
The Body Control Module provides the interface between the V-bus and the E-bus, both of which are CAN bus systems.
- 1. Body Control Module
Turn Signals and Hazard Warning Lights
Two relays are actuated for the turn signals and hazard warning lights (1 for left side and 1 for right side).
When the turn signals flash for the first time (left, right) after the ignition is switched on, the current that is flowing is measured, stored and used as the target value for turn signal bulb monitoring. Because of this procedure it must be ensured that all the turn signals are OK before driving the vehicle.
The trailer turn signal bulbs are also monitored by this procedure when towing.
The turn signal indicator lamps (also for trailers) in the instrument cluster are actuated via the CAN-E bus.
If a bulb is faulty the flashing frequency is doubled.
The acoustic turn signal monitor is generated from the instrument cluster. A warning buzzer in the instrument cluster generates the sound of a switching relay.
External Lighting and Daytime Driving Lamps
The conditions for actuating the external lighting are stored in the Body Control Module. The following are actuated using relays: parking lights, side lights, low beam, high beam, headlamp flash, daytime driving lights, fog lamp and rear fog lamp.
The external lighting can be switched to daytime driving lights and back again (Scandinavia) using the Tech 2.
Instrument Cluster and Switch Illumination Dimming
If the side lights are switched on the instrument cluster lighting can be dimmed (128 levels). The PWM signal (pulse width modulated) is generated by the Body Control Module.
Warning Buzzer Control
- The "Light switched on" warning is activated when: ignition OFF and side lights ON or low beam ON, or high beam ON, or parking lights ON and driver's door is open (door contact closed).
- The "Ignition key inserted (key-in warning)" warning is activated when: ignition OFF and ignition key inserted and terminal W active and driver's door is closed.
- The "Seat belt" (Japan only) warning is active, when: ignition ON and driver's seat belt not being worn (ground signal from switch in belt buckle).
- "Speed exceeded" warning (speed warning, country-specific).
- "Flasher active" feedback (acoustic relay noise simulation).
Courtesy Light Control
- Delayed dimmed activation (fade-in) of courtesy light over a period of approx. 1.5 seconds.
- Delayed dimmed deactivation (fade-out) of courtesy light over a period of approx. 5 seconds.
- Switch-off (timeout) - phase lasts for approx. 10 seconds after closing door without locking it. Timeout starts when fade-in has completed.
- Long shut-off time (big timeout) ensures that the courtesy light is switched off after approx. 30 minutes.
Washer/wiper System Control
Relays performing the switching functions are actuated by the Body Control Module.
- Windshield interval wiping, slow and fast wiping
- Rear window interval wiping
- Windscreen washing
- Rear window washing
- Headlamp washing
- Variable windscreen wiping interval
If there is a fault in the windscreen wiper controller (switch, cable etc.) the windscreen wiper is continuously on.
Variable Windscreen Wiping Interval
The standard interval is approx. 7 seconds. The shortest period that can be selected is approx. 2 seconds and the longest interval period is approx. 15 seconds.
The setting is made after switching the ignition on as follows:
- Switch interval wiping on
- Switch interval wiping off. The time between switching on and switching off is stored by the Body Control Module and becomes the new interval wiping period.
- Switch interval wiping on again.
The duration of a period must be between the shortest and longest periods, otherwise the Body Control Module selects the standard 7-second period. Switching the ignition off and back on again restores the standard period.
If there is a fault in the windscreen wiper controller (switch, cable etc.) the windscreen wiper is continuously on.
Most Important Information from Drive Train to Instrument Cluster
The signals are transmitted via the V-bus to the Body Control Module, from where they are sent to the instrument cluster via the E-bus.
- Engine speed
- Wheel speed
- MTA status
- Brake system
- Service
- Cruise control
- Pre-glow system (diesel)
- Automatic transmission (sport mode)
- Automatic transmission (winter mode)
- Coolant temperature
- Oil pressure
- Odometer
- Traction Control
Other interfaces can be found in the block diagram.