Checking Lambda probes and Lambda control before catalytic converter — AUDI

🧭 Before you start

Fits: Audi A6 C5 (4B)

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

Don't miss

• Connect vehicle diagnostic, testing and information systemVAS 5051 A and select vehicle system "“01 - Engine electronics”" from list. Engine must be idling.
• During basic setting, the activated charcoal filter system solenoid valve N80 is closed and the air conditioner compressor shut off.
• The specification is attained more quickly if the engine speed is increased. The "“Lambda probe status”" display indicates the status of the Lambda control and Lambda probes.
• Do not continue testing until display in zones (1) and (3) has reached "“111”" at least once.
• Fitting locations of connectors .

🔧 Engine codes this applies to

📋 Procedure

1. Connect vehicle diagnostic, testing and information systemVAS 5051 A and select vehicle system "“01 - Engine electronics”" from list. Engine must be idling.
2. From list (1) select diagnostic function "“04 - Basic setting”". [Note: During basic setting, the activated charcoal filter system solenoid valve N80 is closed and the air conditioner compressor shut off.]
3. Use keypad (2) to enter "“030”" for "“Display group number 030”" and confirm by touching the Q key.
4. Check display in zones (1) and (3). [Note: The specification is attained more quickly if the engine speed is increased. The "“Lambda probe status”" display indicates the status of the Lambda control and Lambda probes.]
5. Do not continue testing until display in zones (1) and (3) has reached "“111”" at least once.

6. Switch to "“display group 032”" by touching ↑ key 2 times.
7. Check information shown in display zones (1 ... 4).
8. Check intake system for leaks (unmetered air)
9. Change engine oil or drive car at moderate to high speeds on out-of-town roads
10. Check air mass meter
11. Check solenoid valve for activated charcoal filter
12. Check fuel pressure regulator
13. Check injectors
14. Check Lambda probe heating
15. Check intake system for air leaks and rectify leaks as necessary
16. Check fuel pressure regulator
17. Check air mass meter
18. Check Lambda probe heating
19. Check injectors
20. Check solenoid valve for activated charcoal filter
21. Switch to "“display group 033”" by touching ↑ key.
22. Check information shown in display zones (1 ... 4).
23. Take car for a test drive to free Lambda probe of any deposits, then repeat the test.
24. Check Lambda probe heating before catalytic converter .
25. Check intake system for leaks .
26. Check fuel pressure regulator .
27. Check proper routing of fuel return pipe.
28. Vehicles with engine code "“ARE”", "“AZS”" and "“BES”": Check ageing of Lambda probe before catalytic converter .
29. Check basic voltage
30. Check Lambda probe wiring
31. Check Lambda probe heating
32. Renew Lambda probe
33. Check Lambda probe wiring
34. Unplug 4-pin connector (black) for Lambda probe G39 (bank 1) or 4-pin connector (black) for Lambda probe 2G108 (bank 2). [Note: Fitting locations of connectors .]
35. Connect multimeter (voltage test range) between contacts (3) and (4).
36. Switch on ignition.
37. Switch off ignition.
38. Check Lambda probe wiring.
39. Renew Lambda probe before catalytic converter.
40. 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 .
41. Check the following wiring connections for open circuits.
42. Check following wiring connections for short circuit:
43. Repair wiring connection if necessary.
44. 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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