Oxygen Sensor Heating, Checking

OXYGEN SENSOR HEATING, CHECKING

Special tools, testers and auxiliary items
- VAG 1598/18 test box
- Multimeter (Fluke 83 or equivalent)
- VW 1594 connector test kit
- Wiring diagram

Test conditions
- HO2S relay OK
- Engine coolant temperature at least 80 °C (176 °F)

Test sequence





- Separate 4-pin HO2S harness connector.
- Check resistance of heating circuit at HO2S connector terminals 1 and 2.
Specification: max. 22 Ohms
If the specification is not attained:
- Replace HO2S G39.

If the specification is attained:
- Start engine and run at idle speed.





- Connect multimeter to measure voltage at HO2S connector terminals 1 and 2.

Specification: approx. battery positive voltage (B+)

- Switch ignition off.

If no voltage is present:
- Check wiring from HO2S connector terminals 1 and 2 to relay panel according to wiring diagram.