With Generic Scan Tool

Oxygen sensor heater for oxygen sensor before Three Way Catalytic Converter (TWC), checking

Note: When servicing terminals in harness connector of Heated Oxygen Sensor (HO2S), use only gold-plated terminals.

Recommended special tools and equipment
- VAG 1526 multimeter or VAG 1715 multimeter
- VAG 1594 connector test kit
- Wiring diagram

Test requirements






- The respective fuses of Heated Oxygen Sensor (HO2S) -G39- must be OK.
- Ignition switched off.






- Disconnect 4-pin harness connector (brown) to Heated Oxygen Sensor (HO2S) -G39- (-1-).






- Check oxygen sensor heater for continuity at connector to Heated Oxygen Sensor (HO2S) terminals 1 & 2.

If an open circuit is found in the oxygen sensor heater:

- Replace Heated Oxygen Sensor (HO2S) -G39-.

- Erase DTC memory of Engine Control Module (ECM).

- Generate readiness code.

If oxygen sensor heater has continuity:

- Check voltage supply and wiring.

Voltage supply and wiring, checking






- Set multimeter for voltage measurement and connect it to terminals 1 & 2 at connector to control module.

- Start engine, and let run at idle.

- Measure voltage supply.

- Specified value: oscillating between 0.0 and 12.0 V

If there is no voltage:

- Connect multimeter for voltage measurement to Terminal 1 of connector and engine Ground (GND).

Specified value: 11 to 15 V

If there is no voltage again:

- Check wire connections from Terminal 1 to Fuel Pump (FP) Relay -J17- according to wiring diagram.

If voltage was approximately same as battery voltage:

- Switch ignition off.

- Connect test box to control module wiring harness.

Engine Control Module (ECM) is not connected.






- Check wire between test box and 4-pin connector for open circuit according to wiring diagram.

Terminal 2 & socket 27

Wire resistance: max: 1.5 Ohms

If no wiring faults are found:

- Replace Engine Control Module (ECM).