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.
Functional description
Even while the engine is off, it remains vital to ensure that power assistance is available for the braking system. To this end the brake servo booster is equipped with a brake vacuum sensor. The brake vacuum sensor is connected to the engine control (DME or DDE or EME).
- DME stands for Digital Motor Electronics
- DDE stands for Digital Diesel Electronics
- EME stands for Electrical Machine Electronics
As soon as the vacuum in the system drops below a specific threshold value, an automatic engine start is carried out or the electrical vacuum pump is activated, depending on the series and on the engine version.
| Item | Explanation |
|---|---|
| 1 | Brake servo |
| 2 | Brake vacuum sensor |
| 3 | three pin plug connection |
Within the brake vacuum sensor a sheet-metal diaphragm converts vacuum into a travel distance. Four pressure-sensitive resistors convert this travel into a voltage signal, which is sent to the engine control (DME or DDE or EME).
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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.