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
Brake lights (10/43 and 10/50) are activated by closing of the brake light switch (3/9). A directly connected signal is sent to Central electronic module (CEM) (4/56) that the brake is activated. The directly connected signal is also sent on by Central electronic module (CEM) to Engine control module (ECM) (4/46) via connector 74/301. Engine control module (ECM) uses the directly connected signal to generate a CAN-signal which, among others, is used by Brake control module (BCM) (4/16).
The lights are powered directly via an output on the central electronic module (CEM).
Information about the lamp circuit is extracted via the power supply function in the central electronic module (CEM).
In the event of a fault, the central electronic module (CEM) transmits data via the Control area network (CAN) to the driver information module (DIM) (5/1) which displays a text message.
In order to reduce the number of collisions from behind during sudden braking there is a function, emergency brake lights, in the central electronic module (CEM) that can activate the hazard warning flashers and position lights, or allow the brake lights to flash instead of being constantly on. The configuration and functioning of this function are market-dependent and also differ between vehicle models.
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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.
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