Checking signal from brake light switchF and brake pedal switch F47. — VW

🧭 Before you start

Fits: platform code 6N1

• Renewed: brake light switchf, engine control unit

Don't miss

• Operate brake pedal slowly. Both displays must simultaneously switch from 0 to 1.

🔧 Engine codes this applies to

📐 18 workshop diagrams for AGD

Real factory drawings for this job — timing marks, bolt locations and routing. Locked in the free view.

📋 Procedure

1. Connect fault readerV.A.G 1551 or vehicle system testerV.A.G 1552 and select engine electronics control unit with "“address word 01”". The ignition must be switched on for this purpose. (Connecting fault readerV.A.G 1551 and selecting engine electronics control unit ).
2. Press keys 0 and 8 for function "“Read measured value block”" and confirm entry with Q key.
3. Press keys 0, 0 and 6 for "“Display group number 6”" and confirm entry with Q key.
4. Observe display in display zone 2.
5. Operate brake pedal slowly. Both displays must simultaneously switch from 0 to 1.

6. Release brake pedal slowly into rest position again.
7. Press → key.
8. Press keys 0 and 6 for function "“End output”" and confirm entry with Q key.
9. Switch off ignition.
10. Remove cover in footwell (driver side).
11. Pull 4-pin connector off brake light switchF and brake pedal switch F47.
12. Measure resistance between switch contacts 1 + 4.
13. Measure resistance between switch contacts 2 + 3.
14. Renew brake light switchF and brake pedal switch F47.
15. Connect adapter cable, 121-pinV.A.G 1598/31 to control unit wiring harness. The engine control unit remains disconnected.
16. Check wiring between 121-pin adapter cableV.A.G 1598/31 and 4-pin connector for open circuit according to current flow diagram. Contact 2 + socket 1 Contact 2 + socket 2 Contact 3 + socket 65 Contact 4 + socket 32.
17. Check the line between 4-pin connector contact 1 and central electrics according to current flow diagram:
18. Also check wiring for short to one another, short to vehicle earth and short to battery positive.
19. Renew engine control unit .

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