Checking Lambda probe heating Z29 for Lambda probe after catalytic converter — AUDI

🧭 Before you start

Fits: Audi TT Mk1 (8N)

• Special tools named: V.A.G 1598/31
• Renewed: lambda probe, engine control unit removing

Don't miss

• The point at which the engine control unit switches the Lambda probe heating on and off can be observed in display zone 4 of "“measured value block 041”".
• Connect adapter cable, 121-pin V.A.G 1598/31 (test box) to wiring harness for engine control unit, but do not connect the engine control unit itself .

🔧 Engine codes this applies to

📐 38 workshop diagrams for ARY

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

📋 Procedure

1. Unbolt the protective cover (arrows).
2. Unplug 4-pin connector (brown) for Lambda probe after catalytic converter G130.
3. Connect multimeter (resistance measurement range) between contacts (1) and (2).
4. Renew Lambda probe after catalytic converter.
5. Check voltage supply for Lambda probe heating.

6. Connect multimeter (voltage measuring range) between contacts (1) (positive) and (2) (earth).
7. Start engine. [Note: The point at which the engine control unit switches the Lambda probe heating on and off can be observed in display zone 4 of "“measured value block 041”".]
8. Connect multimeter (voltage measuring range) between contact (1) (positive) and vehicle earth.
9. Operate the starter briefly.
10. Refer to current flow diagram to check for open circuit in wiring from contact (1) of connector via fuse to fuel pump relay.
11. Connect multimeter (voltage measuring range) between contact (2) (switched earth connection from engine control unit) and battery positive.
12. Start engine. [Note: The point at which the engine control unit switches the Lambda probe heating on and off can be observed in display zone 4 of "“measured value block 041”".]
13. Switch off ignition.
14. Connect adapter cable, 121-pin V.A.G 1598/31 (test box) to wiring harness for engine control unit, but do not connect the engine control unit itself .
15. Check for open circuit in the following wiring connection:
16. Repair wiring connection if necessary.
17. Renew engine control unit Removing and installing engine control unit without protective housing or Removing and installing engine control unit with protective housing.

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