Checking coolant temperature sender: VW Passat B5 2.3 (AZX)

🧭 Before you start

Connect the fault reader, select the engine control unit and read display group 4 while the engine warms at idle. If the value does not rise evenly, pull the 4-pin connector, bridge contacts 3 and 4 and watch the display. Then check the wiring between the test box and the connector for open and short circuits, measure the sender resistance, and renew the sender or, as a last step, the control unit. Read and clear the fault memory at the end.

Fits: VW Passat B5 (3B)

• Special tools named: V.A.G 1551, V.A.G 1552, V.A.G 1598/31
• Renewed: engine control unit

Don't miss

• The temperature reading must rise uniformly at idle; it moves in steps of 1.0 °C.
• Leave the engine control unit disconnected while the test box is on the harness.
• Check both lines for short to battery positive as well; specification is infinite resistance.
• Renewing the control unit is the last step, only after sender and wiring check out.
• Read and clear the fault memory once the repair is done.

Written for this job from the workshop steps below · TorqFix editorial.

🔧 Engine codes this applies to

📋 Procedure

1. Connect fault reader V.A.G 1551 (V.A.G 1552). Then switch ignition on and select engine control unit with "“Address word”" 01. (Connect fault reader and select engine 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 4 for "“Display group number 4”" and confirm entry with Q key.
4. Read off coolant temperature value in display zone 3.
5. Start engine and run at idling speed. The temperature value must increase uniformly

6. Press → button.
7. Press buttons 0 and 6 for function "“End output”" and confirm entry with Q button.
8. Switch off ignition.
9. Renew coolant temperature sender G62 with coolant temperature display sender G2. [Note: Temperature increases in steps of 1.0°C.]
10. Read fault memory, if necessary, repair any faults and then clear fault memory , Reading and clearing fault memory.
11. Continuation
12. Continuation
13. Pull 4-pin connector off coolant temperature sender G62 with coolant temperature display sender G2(arrow).
14. Bridge connector contacts 3+4 with auxiliary cables fromV.A.G 1594 and observe display.
15. Press → button.
16. Press buttons 0 and 6 for function "“End output”" and confirm entry with Q button.
17. Switch off ignition.
18. Renew coolant temperature sender G62 with coolant temperature display sender G2.
19. Press → button.
20. Press buttons 0 and 6 for function "“End output”" and confirm entry with Q button.
21. Switch off ignition.
22. Check lines according to current flow diagram .
23. Pull 4-pin connector off coolant temperature sender G62 with coolant temperature display sender G2(arrow).
24. Press → button.
25. Press buttons 0 and 6 for function "“End output”" and confirm entry with Q button.
26. Switch off ignition.
27. Renew coolant temperature sender G62 with coolant temperature display sender G2.
28. Read fault memory, if necessary, repair any faults and then clear fault memory , Reading and clearing fault memory.
29. Press → button.
30. Press buttons 0 and 6 for function "“End output”" and confirm entry with Q button.
31. Switch off ignition.
32. Check lines according to current flow diagram .
33. Connect test box V.A.G 1598/31 to control unit wiring harness. The engine control unit remains disconnected.
34. Pull 4-pin connector off coolant temperature sender G62 with coolant temperature display sender G2(arrow).
35. Check lines between test box and 4-pin connector for open circuit referring to current flow diagram.
36. Check line between test box and 4-pin connector contact 3 to line contact 4 and to vehicle earth using current flow diagram.
37. Additionally check both lines for short-circuit to battery positive. Specification: ∞Ω
38. Measure resistance at contact C (signal) and D (earth) on coolant temperature sender G62.
39. Renew coolant temperature sender G62 with coolant temperature display sender G2.
40. Read fault memory, if necessary, repair any faults and then clear fault memory , Reading and clearing fault memory.
41. Renew engine control unit .

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