Brake light switch and brake vacuum vent valve switch, checking: Notes
WARNING: This page is about a different car, the 1999 Volkswagen Jetta, 1998 Volkswagen Jetta, and 1997 Volkswagen Jetta. However, it is still accessible from the selected car via links, so may be relevant.
Because the Diesel injection system uses a throttle position sensor that could malfunction, for reasons of safety, the engine is regulated when the brakes are applied. The Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) requires signals from the brake light switch and the brake vacuum vent valve switch for this function.
If the brakes are operated while the accelerator pedal remains in a constant position, engine speed is immediately reduced to idle. Incorrectly adjusted switches could lead to unnecessary control.