Checking HO2S Probe Heating Circuit

Heated Oxygen Sensor Connector:

- Disconnect HO2S heater harness connector - 2.
^ Location: connector bank on bulkhead.

2-Pin Connector:

- Connect Digital Volt Ohm Multimeter (DVOM) between: terminals 1 and 2 of HO2S heater harness connector, using adapter cables from connector test kit VW 1594.
- Start engine and let idle.
^ Must be 12-14 volts.

If NOT:
- Check HO2S circuit breaker -S73- in auxiliary relay panel 2, right A-pillar.
- Check continuity (according to wiring diagram) between terminal 2 and HO2S circuit breaker -S73-.
^ Must be 0.5 ohm maximum (if necessary, check terminal assignments).
- Check continuity between terminal 1 and engine Ground (GND).
^ Must be 0.5 ohm maximum.

Central Electric Panel With Detail Of Relay Position 6:

- Check continuity (according to wiring diagram) between HO2S circuit breaker -S73- and terminal 30 of fuel pump relay -J17- (relay location 6).
^ Must be 0.5 ohm maximum.

If circuit is open:
- Perform necessary repairs.

If circuit is NOT open:
- Switch DVOM to 10A (DC) measuring range.

Heated Oxygen Sensor Connector:

- Connect additional test cable VW 1315 A/1 to harness connector position 2.
- Start engine and let idle.
^ Must be 0.5 - 3.0 amps.

Note:
Current decreases as sensor temperature increases.

If specified value is NOT obtained:
- Replace HO2S sensor probe.