Brake Signal: Testing and Inspection

Signal From Brake Light Switch and Brake Pedal Switch, Checking

Special tools and equipment
- V.A.G 1551 scan tool or 1552 scan tool with cable VAG 1551/3
- Test box VAG 1598/31
- Hand multimeter VAG 1526 or multimeter VAG 1715
- Adapter set VAG 1594
- Wiring diagram

Check conditions






- All fuses must be OK.
- The battery voltage must be at least 11.5 V.
- All electrical consumers, e.g. lights and rear window heating must be switched off

Test sequence
- Connect the V.A.G 1551 scan tool ((VAG 1552). Then switch ignition on and select engine control module with the "Address word" 01. [1][2]Reading and Clearing Diagnostic Trouble Codes

Indicated on display:

Rapid data transfer HELP
Select function XX

- Press keys 0 and 8 for the function "Read measuring value block" and confirm entry with Q key.

Indicated on display:

Read measuring value block
Input display group number XXX

- Press keys 0, 6 and 6 for "display group 66" and confirm with Q key.

Indicated on display:

Read measuring value block 66 ->
1 2 3 4

- Observe display in display zone 2: (3rd and 4th positions from left)
Specification: x x 0 0

- Depress brake pedal fully and observe display in display zone 2.
Specification: x x 1 1

- Press the -> key.
- Press keys 0 and 6 for the "End output" function and confirm input with the Q key.
- Switch off ignition.

If the specification is not obtained:
- Remove the shelf on driver's side:
- Pull the connector off brake light/brake pedal switch.






- Connect the multimeter to measure resistance between contacts 1 and 4.
Specification: Infinity Ohms (no continuity)

- Depress brake pedal.
Specification: approx. 0 Ohms

- Connect the multimeter to measure resistance between contacts 2 and 3.
Specification: approx. 0 Ohms

- Depress the brake pedal.
Specification: Infinity Ohms (no continuity)

If the specifications are not attained:
- Replace the brake light/brake pedal switch.
- Check DTC memory, if necessary, repair any faults and then erase DTC memory.
Reading Diagnostic Trouble Codes
Clearing Diagnostic Trouble Codes

If the specifications are obtained:






- Connect multimeter to measure voltage between contact 1 and Ground.
Specification: at least 11.5 V

- Switch ignition on.
- Connect the multimeter to measure voltage between contact 2 and Ground.
Specification: at least 11.5 V

If the specifications are not obtained:
- Check wiring between 4-pin connector contacts I and 2 and multi-function unit using wiring diagram.

If the specification is obtained:
- Remove wiper arms and cowl panel






- Connect test box VAG 1598/31 to control module wiring harness. The engine control module remains disconnected.






- Check wiring for open circuit between test box and 4-pin connector using wiring diagram.
Contact 2 and test box socket 55
Contact 4 and test box socket 56
Wire resistance: max. 1.5 Ohms

- Additionally check wires for short to one another.
- Additionally check the wiring for short to battery positive or Ground.

If no fault is detected in the pipes:
- Replace engine control module.