With Manufacturer's Scan Tool

Brake Light Switch -F- And Brake Pedal Switch -F47-







Special tools and workshop equipment required
- V.A.G 1526 A Multimeter
- V.A.G 1527 B LED voltage tester
- V.A.G 1594 A Connector test kit
- V.A.G 1598/31 Test box
- VAS 5051 Vehicle diagnostic, testing and information system
- VAS 5051/1 Adapter

NOTE: Command from Sender -2- for accelerator pedal position -G185- (potentiometer) to Engine Control Module (ECM) for opening throttle valve is suppressed for safety reasons when brake is pressed. To do so the brake light signal and also the Brake Pedal Switch -F47- signal are required in the ECM. 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 actions.

Work sequence
- Connect VAS 5051 scan tool and select vehicle system "01 -Engine electronics" in selection.

When doing this the ignition must be switched on.







Display on VAS 5051:
- Under -1- select diagnostic function "08 - Read measured value block".







Display on VAS 5051 scan tool:
1. Enter display group
- Enter "066" for "display group number 066" in field -2- and confirm entry by pressing -Q- button.







Display on VAS 5051 scan tool:
- Check Brake Light Switch -F- / Brake Pedal Switch -F47- in display field -2-.







- Exit function "08 - Read measured value block" by pressing square button.

If the display is not as described:

Check switch
- Remove driver's storage compartment:







- Disconnect connector from Brake Light Switch -F- / Brake Pedal Switch -F47- -2-.







- Connect multimeter between terminals 1 and 4 to measure resistance.

Specified value: Infinite Ohms (no continuity)

- Press brake pedal.

Specified value: approx. 0 Ohm

Connect multimeter between terminals 2 and 3 to measure resistance.

Specified value: approx. 0 Ohm

Press brake pedal.

Specified value: Infinite Ohms(no continuity)

If the specified values are not obtained:
- Replace Brake Light Switch -F- / Brake Pedal Switch -F47-.

If specifications are obtained:

Check power supply







- Connect voltage tester V.A.G 1527 B as follows:

Connector Measure to
terminal
1 Vehicle body ground (GND) point

- LED must light up.

Connector Measure to
terminal
3 Vehicle body ground (GND) point

- Switch ignition on.
- LED must light up.

If LED does not light up:
- Check wiring for open circuit and repair if needed.

If LED lights up:

Check activation
- Connect test box V.A.G 1598/31 to wiring harness for Engine Control Module (ECM); do not connect Engine Control Module (ECM).







- Check for open circuit and short to positive or ground (GND) in following wiring connections:

Connector Test box V.A.G 1598/31
terminal Socket
2 55
4 56

- Repair any open/short circuit as needed.