Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Brief description of components
The following components deliver an input signal for the electrical adjustment of the exterior mirrors:
- Driver's door switch block
The two exterior mirrors are operated from the driver's door switch block.
- up to 09/2005
The switch block is connected via a LIN bus on the driver's door module (TMFA) (LIN = Local Interconnect Network).
- from 09/2005
The driver's door switch block is connected to the body gateway module (KGM) via the LIN bus (LIN = Local Interconnect Network).
- Position potentiometer in exterior mirror
The mirror glass is adjusted horizontally and vertically by separate motors. The position of the motors is detected by potentiometers.
- up to 09/2005
The position is sent to the relevant door module.
- from 09/2005
Information about the position is sent to the body gateway module.
The following control units are involved in the operation of the exterior mirrors:
- TMFA and TMBF: Driver's door module and front passenger door module
- up to 09/2005
The door modules control the exterior mirrors. The driver's door module (TMFA) receives the operation request for the exterior mirrors from the switch block in the driver's door.
- from 09/2005
The body gateway module actuates the exterior mirrors: The door modules and byteflight are discontinued.
- SGM: Safety and gateway module
- up to 09/2005
The safety and gateway module (SGM) forms the gateway between K-CAN and byteflight.
- Body gateway module
- from 09/2005
The body gateway module (KGM) is the central gateway in the bus system. The KGM actuates the exterior mirrors.
- SMFA: Seat module, driver
The driver's seat module (SMFA) activates the seat memory and the driver's mirror memory. The message is sent to the door modules on the K-CAN.
- SH: Independent heating
The independent heating control unit uses the K-CAN to report independent heater operation. Exterior mirror heating is activated during independent heater operation.
The following information is also required:
- EGS or LM:Electronic transmission control (with automatic transmission) or light module (with manual transmission)
The reverse-gear signal is delivered by the transmission control (PT-CAN) or the light module (K-CAN). The reverse-gear signal is required for the automatic parking function.
- AHM: Trailer module
The trailer module (AHM) sends a signal indicating whether or not the vehicle is towing a trailer. The automatic parking function is deactivated if a trailer is detected.
The following motors are controlled to provide the exterior mirror functions:
- Motors for adjusting the mirror glass horizontally and vertically
One motor adjusts the mirror glass horizontally, another adjusts the mirror glass vertically. The mirror is adjusted by reversing the motor's direction of rotation.
- Motor for folding in the mirrors
The exterior mirror consists of a mirror base and mirror body. The motor for folding the mirror body in and out is fitted in the mirror base.
The mirror is folded in and out by reversing the motor's direction of rotation.
- Mirror heating
The mirror heating defrosts the mirror glass in the exterior mirrors.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.