Checking relay for fuel cooling pump V166: Audi A8 D2 3.3 TDI (AKF)

🧭 Before you start

Fits: Audi A8 D2 (4D)

• Renewed: engine control unit, fuel cooling pump

🔧 Engine codes this applies to

📋 Procedure

1. In list (1) select function "“03 - Final control diagnosis”".
2. Keep touching → key until fuel cooling pump relay J445 is actuated.
3. Terminate function "“03 - Final control diagnosis”" by touching ← key and switch off ignition.
4. Check power supply of fuel cooling pump relay J445.
5. Check actuation of fuel cooling pump relay J445.

6. Check power supply for fuel cooling pump V166.
7. Take out floor covering in front right footwell.
8. Screw out bolts for electronics box cover (arrows) and detach cover.
9. Detach fuel cooling pump relay J445(arrow).
10. First connect up multimeter (voltage measuring range) between relay socket contact (2) and earth and then between relay socket contact (6) and earth.
11. Switch on ignition.
12. Use current flow diagram to repair wiring.
13. Connect up voltage testerV.A.G 1527 B between relay socket contact (4) and battery positive.
14. Repeat function "“03 - Final control diagnosis”".
15. Keep touching → key until fuel cooling pump relay J445 is actuated.
16. Terminate function "“03 - Final control diagnosis”" by touching ← key and switch off ignition.
17. Replace fuel cooling pump relay J445.
18. Switch off ignition.
19. Slacken off cross-head bolts (1) at electronics box in plenum chamber.
20. Unclip plenum chamber cover (2) at front at bulkhead (arrows).
21. Detach plenum chamber cover.
22. Prise out cover (1) in scuttle panel trim and slacken off rear cross-head bolt (rear right arrow).
23. Slacken off the remaining cross-head bolts (arrows).
24. Detach cover for electronics box in plenum chamber.
25. Screw out bolt (arrow).
26. Disengage retainer.
27. Detach diesel direct injection system control unit 2J494(Item 2). Release and unplug connectors.
28. With ignition switched off, connect test boxV.A.G 1598/30 to connectors of diesel direct injection system control unit 2J494 only (not to actual control unit).
29. Check for open circuit and short to earth or positive in the following wiring:
30. Repair wiring if necessary.
31. Replace engine control unit.
32. On vehicles with auxiliary heater, screw out bolts (arrows) for attaching exhaust pipe of auxiliary/supplementary heater to noise insulation.
33. Unfasten quick-release fasteners (1) and detach front noise insulation.
34. Unplug connector (arrow) at fuel cooling pump.
35. Connect up voltage testerV.A.G 1527 B between contacts (1) and (2).
36. Repeat function "“03 - Final control diagnosis”".
37. Keep touching → key until fuel cooling pump relay J445 is actuated.
38. Terminate function "“03 - Final control diagnosis”" by touching ← key and switch off ignition.
39. Check for open circuit in wiring between connector of fuel cooling pump and fuel cooling pump relay J445 (in electronics box in passenger's footwell).
40. Check for open circuit in wiring between connector of fuel cooling pump V166 and earth point.
41. Replace fuel cooling pump.

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