With Manufacturer's Scan Tool

Signal From Brake Light Switch -F- And Brake Vacuum Vent Valve Switch -F47-, Checking

Special tools, test equipment and auxiliary items
- VAG 1551 scan tool or VAG 1552 mobile scan tool with VAG 1551/3B cable
- VAG 1598/31 test box
- VAG 1526 hand multimeter or VAG 1715 multimeter
- VAG 1594 adapter set
- Electrical Wiring Diagram

Test conditions






- All fuses must be OK
- Battery voltage must be at least 11.5 V
- Brake lights functioning OK
- All electrical accessories, e.g. lights and rear window defroster must be switched off
- Selector lever must be in position "P" or "N" on vehicles with an automatic transmission

Test sequence
- Connect VAG 1551 scan tool ((VAG 1552). Switch ignition on and select Motronic Engine Control Module (ECM) -J220- with "Address word" 01.
Indicated on display

Rapid data transfer HELP
Select function XX

- Press buttons -0- and -8- for function "Read measuring value block" and confirm entry with -Q- button.

Indicated on display

Read measuring value block HELP
Input display group number XXX

- Press buttons -0-, -6- and -6- for "display group 66" and confirm with -Q- button.

Indicated on display (1 to 4 = Display zones)

Read measuring value block 66 ->
1 2 3 4

- Observe display in display zone 2: (1st and 2nd positions from right) Brake pedal not depressed:
Specification: x x x x x x 0 0

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

- Press -> button.
- Press buttons -0- and -6- for "End output" function and confirm input with -Q- button.
- Switch off ignition.

If the display does not change:
- Remove driver's side footwell cover.
- Disconnect 4-pin connector from Brake Light Switch -F- and Brake Vacuum Vent Valve Switch -F47-.






- Measure resistance between terminals 1 + 4 of switch.
Specification:
- Brake pedal not depressed: Infinity Ohms (no continuity)
- Brake pedal depressed: Max. 1.5 Ohms

- Measure resistance between terminals 2 + 3 of the switch.
Specification: 0 Ohms
- Brake pedal not depressed: Max. 1.5 Ohms
- Brake pedal depressed: Infinity Ohms (no continuity)

If the specifications are not obtained:
- Replace Brake Light Switch -F- and Brake Vacuum Vent Valve Switch -F47-.
- Check DTC Memory, if necessary, repair any malfunctions and then Erase DTC Memory.
- Read readiness code. If DTC memory has been erased or Motronic Engine Control Module (ECM) -J220- was disconnected from battery positive, readiness code must be generated again.

If the specifications are obtained:






- Connect multimeter to measure voltage between terminal 1 and Ground (GND).
Specification: at least 11.5 V

- Connect multimeter to measure voltage between terminal 2 and Ground (GND).
- Switch on ignition.
Specification: min. 11.5 V

If the specifications are not obtained:
- Check wiring between 4-pin connector terminals 1 and 2 to central electrics using Electrical Wiring Diagram.

If the specifications are obtained:
- Remove inner plenum chamber cover, left.






- Connect VAG 1598/31 test box to control module wiring harness. Motronic Engine Control Module (ECM) -J220- is not connected by this action.






- Check wiring for open circuit between test box and 4-pin connector using Electrical Wiring Diagram.
- terminal 3 + socket 55
- terminal 4 + socket 56
Wire resistance: Max. 1.5 Ohms

- Also check wires for short to one another.
- Also check wiring for short to battery positive or Ground (GND).

If no wiring malfunction is found:
- Replace Motronic Engine Control Module (ECM) -J220-.