Brake light switch and brake pedal switch, checking: Notes

The diesel injection system operates with a throttle position sensor. For safety reasons, the engine is regulated when the brakes are operated. The ECM requires signals from the brake light switch and also the brake pedal switch. This means that if the brakes are operated when the accelerator pedal is held at a constant position, the engine is immediately reduced to idling speed. Incorrectly adjusted switches may lead to unwanted regulating action.

Special tools, testers and auxiliary items required 

• V.A.G 1551/1552 with adapter cable V.A.G 1551/3
• Test box V.A.G 1598/22 (through my 1999)
• Test box V.A.G 1598/31 (from my 2000)
• Digital multimeter US 1119 (Fluke 83 or equivalent)

• Adapter set V.A.G 1594
• Wiring diagram