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The lights are controlled by footwell module, FRM, the windows are controlled by various modules but the FRM is also a major player in the window operation.
check fuses F33, F34, F23, F96
System functions
The footwell module picks up the signals from the doors and controls the lighting. The footwell module is also the interface to the instrument cluster. Depending on the equipment version, the footwell module picks up the following signals:
Height-level sensor
Reversing light switch
Brake-light switch
Hazard warning lights switch
Light switch
Switch block, driver's door
Door contacts
Driver's door lock
The following functions are controlled by the footwell module:
Communication between the LIN bus and body CAN
Storing vehicle order
Exterior mirrors
Exterior lights
Interior lights
Central locking
Front power windows
Communication
The footwell module enables communication to take place between the LIN bus and the body CAN.
Storing vehicle order
The vehicle order is stored in the footwell module. The vehicle order enables the vehicle to be identified. Besides the type code number, the vehicle order contains all important equipment features on the vehicle.
Exterior mirrors
There are two equipment variations of the switch block in the driver's door:
Basic version of the driver's door switch block
The switch block sends its signals directly to the footwell module.
High version of the driver's door switch block
This switch block is connected to the LIN bus. The requests to adjust the exterior mirrors are sent via the LIN bus.
Exterior lights
The lighting functions are integrated into the footwell module. These lighting function are:
Sidelights
Low beam
High beam
Headlamp flasher
Fog lamps
Rear fog light
Turn signals
Hazard warning lights
Brake light
Reversing lights
Parking light
Besides the lighting functions, other exterior lighting functions are also integrated in the footwell module:
Light monitoring
Headlight vertical aim control
Emergency operating mode if the footwell module should fail
Lamp replacement
Home lighting
Visual alarm after anti-theft alarm has been triggered
Actuation of bi-xenon headlamps
All lighting functions except the additional brake light are activated with pulse-width modulated signals by the footwell module. These pulse-width modulated signals enable a uniform brightness of the exterior lighting.
Interior lights
On vehicles without a roof control panel, the footwell module actuates the interior lighting in the roof area directly. All footwell module outputs for interior lighting are pulse-width modulated. With standard equipment, the interior lighting comprises the following components:
Front interior light
Luggage compartment lights
Glove compartment lighting
Footwell lighting
The following components can also be installed as optional extra for the interior lights:
Rear interior light
Courtesy lighting
Central locking
The footwell module evaluates the status of the Hall sensors in the door contacts. When the vehicle is locked or unlocked with the mechanical key element, the footwell module will recognise this request. The footwell module sends a message on the body CAN to the Comfort Access.
Power windows
The footwell module and the junction box electronics activate the power window drives. The relays for the front power window motors are located in the footwell module.
Notes for Service department
The following information on the footwell module is available for service staff:
Notes on coding / programming
Nearly all Car and Key Memory functions are programmed inside the vehicle itself.
No liability can be accepted for printing or other errors. Subject to changes of a technical nature
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