Checking Lambda probe heating for Lambda probes before catalytic converter — VW

🧭 Before you start

Fits: VW Passat B5 (3B)

• Special tools named: V.A.G 1551, V.A.G 1552, V.A.G 1594, V.A.G 1598/31

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• Lambda probe heating may be switched on or off depending on the engine's operating status, i.e. the displays in display zone 2 may show either Htg.b(a)C.ON or alternatingly Htg.b(a)C.ON/Htg.b(a)C.OFF.

🔧 Engine codes this applies to

📋 Procedure

1. Connect fault reader V.A.G 1551 (V.A.G 1552). Start engine and select "“Address word”" 01 of engine control unit. (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, 4 and 1 for "“Display group number 41”" and confirm entry with Q keys.
4. Check specification for Lambda probe heating in display zone 2. [Note: Lambda probe heating may be switched on or off depending on the engine's operating status, i.e. the displays in display zone 2 may show either Htg.b(a)C.ON or alternatingly Htg.b(a)C.ON/Htg.b(a)C.OFF.]
5. Press → button.

6. Press buttons 0 and 6 for function "“End output”" and confirm entry with Q button.
7. Switch off ignition.
8. Disconnect 6-pin connector (black) (1) to Lambda probe before catalytic converter G39.
9. Set multimeter to resistance measurement and check resistance of probe heating at connector to Lambda probe between contacts 3+4; specification: 2.5...10.0 Ω
10. Renew Lambda probe before catalytic converter G39.
11. Connect multimeter with auxiliary cables from V.A.G 1594 to measure voltage at contacts 3+4 (connector to engine control unit).
12. Start engine and run at idling speed.
13. Measure voltage supply and observe display group 42, display zone 2.
14. Switch off ignition.
15. Connect test box V.A.G 1598/31 to control unit wiring harness. The engine control unit remains disconnected.
16. Check line between test box and 6-pin connector for open circuit referring to current flow diagram. Contact 4+socket 5 line resistance: Max. 1.5 Ω
17. Check line between 6-pin connector contact 3 and fuel pump relay J17 for open circuit using current flow diagram. Cable resistance: max. 1.5 Ω.

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