Checking Oxygen Sensor Heating

PROCEDURE
- Disconnect Heated Oxygen Sensor (HO2S) harness connector on right or left cylinder bank.

2 Pin Harness Connector:

- Connect multimeter (Fluke 83 or equivalent) between connector terminals 1 (GND), and 2 (B+).
- Start engine and let idle.
^ Specified value: approx. 12-14 volts.

If specified values are not obtained:
- Check HO2S fuse S28 (red fuse holder, engine) in central electrical system.
- Check continuity in wiring from connector terminal 1 to fuse using wiring diagram.
^ Specified value: maximum 0.5 ohms.
- Check continuity in wiring from connector terminal 2 to GND.
^ Specified value: maximum 0.5 ohms.
- Check fuel pump relay.

If the specified values are obtained:
- Connect additional test harness VAG 1315A/1 into 2-pin HO2S connector.
- Switch multimeter to 10 amp (DC) measuring range and connect (connect test harness to 10 amp connector).
- Start engine and let idle.
^ Specified reading: 0.5-3.0 amps.
^ Current (amperage) decreases as sensor temperature increases.

If specified reading is not obtained:
- Replace heated oxygen sensor.