Brake Signal: Testing and Inspection

Brake Light Switch and Brake Pedal Switch Signal Check

Special tools and equipment
- V.A.G1551/1552 Scan Tool (ST) with VAG1551/3 adapter cable
- VAG1598/22 test box
- Multimeter (Fluke 83 or equivalent)
- VW1594 adapter set
- Wiring diagram

Test sequence
- Connect V.A.G1551 (VAG1552) Scan Tool (ST). [1][2]Reading and Clearing Diagnostic Trouble Codes
- Switch ignition on and press buttons -0- and -1- to insert "Engine Electronics" address word 01.

Indicated on display

Rapid data transfer HELP
Select function XX

- Press buttons -0- and -8- to select "Read Measuring Value Block" function 08 and press -Q- button to confirm input.

Indicated on display

Read Measuring Value Block HELP
Input display group number XXX

- Press buttons -0-, -6- and -6- to input display group number 66 (066) and press -Q- button to confirm input.

Indicated on display: (1-4 = display fields)

Read Measuring Value Block 66 ->
1 2 3 4

- Observe display in display field 2 (3rd and 4th positions from left):
Specified value: x x 0 0

- Depress brake pedal and observe display in display field 2.
Specified value: x x 1 1

- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06 and press -Q- button to confirm input.
- Turn off ignition.

If the display does not change:
- Disconnect 4-pin harness connector from brake light switch and brake pedal switch.






- Measure resistance between terminals -1- + -4- of switch.
Specified value with brake pedal not depressed: Infinity ohms
Specified value with brake pedal depressed: max. 1.5 ohms

- Measure resistance between terminals -2- + -3- of switch.
Specified value with brake pedal not depressed: 1.5 ohms
Specified value with brake pedal depressed: max. Infinity ohms

If the specified values are not obtained:
- Replace brake light switch -F- and brake pedal switch -F47-.

- Check DTC memory. If necessary, repair any malfunctions and erase DTC memory.
Reading Diagnostic Trouble Codes
Clearing Diagnostic Trouble Codes

- Display readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
If DTC memory has been erased or the Engine Control Module (ECM) was disconnected from permanent battery (B+) voltage, generate the readiness code again. Monitors, Trips, Drive Cycles and Readiness Codes

If the specified values are obtained:
- Remove wiper arms and plenum chamber cover.






- Connect VAG1598/22 test box to control module wiring harness.






- Check wiring between test box and 4-pin harness connector for open circuit according to wiring diagram.
- Terminal -3- + socket 48
- Terminal -4- + socket 47
Wire resistance: max. 1.5 ohms

If the specified value is obtained:
- Check wire between 4-pin harness connector terminals -1- + -2- and Fuel Pump (FP) relay -J17- for open circuit according to wiring diagram.
Wire resistance: max. 1.5 ohms