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.
Brake light switch
Together with the signal from the brake pressure sensor, braking operations are detected. Two Hall effect sensors as switches are installed in the brake light switch: the brake light switch and the brake light test switch (redundancy for safety reasons). The signals indicate whether the brake pedal has been pressed. The data interchange is digital.
| Index | Explanation |
|---|---|
| 1 | Brake light switch |
| 2 | Plug connection |
The two redundant signals from the brake light switch are read in by the Car Access System (CAS). The CAS forwards the signals on the bus system, e.g. for the engine control system.
The signals from the brake light switch are hard-wired and branched off for the following systems:
- Dynamic Stability Control (DSC) for the brake intervention
- Footwell module (FRM) for reversing light
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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.