Oxygen Sensor (O2S) and Oxygen Sensor Control Behind Three Way Catalytic Converter (TWC), Checking

Oxygen Sensor and oxygen sensor control behind 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) -G130- must be OK.
- Battery voltage must be at least 11.5 volts.
- All electrical consumers like, for example, lights and rear window heating must be switched off.
- Parking brake must be engaged or else daylight driving lights will be switched on.
- If vehicle is equipped with an A/C system, it must be switched off.
- Ground (GND) connections between engine and chassis must be OK.
- Exhaust system must be properly sealed between catalytic converter and cylinder head.
- Coolant temperature must be at least 80 � C.
- Oxygen sensor heater for oxygen sensors behind catalytic converter must be OK.

Function test

- Select the following output of oxygen sensor signals and check whether the specified values are being reached.

- Check the specified values of the output of oxygen sensor signals at idle:






If specified values are obtained:

- End diagnosis and switch ignition off.

If specified values are not obtained:

- End diagnosis and let engine continue to run at idle.

- Check primary voltage.

Checking primary voltage






- Disconnect 4-pin harness connector (black) to Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130- (-1-).






- Use adapter cables from V.A.G 1594 to connect multimeter to terminals 3 & 4 (Motronic ECM connector) for voltage measurement.

- Start engine and measure primary voltage.

Specified value: 0.40 to 0.50 volts

- Switch ignition off.

If specified value is not obtained:

- Test oxygen sensor wires.

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

- Generate readiness code.

If specified value is obtained:

- Replace Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130-.

Checking oxygen sensor wires

- Connect test box to control module wiring harness.






- Check wires between test box and 4-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.

Wire resistance: max: 1.5 Ohms






- Also check wires for short circuit to B+ and Ground (GND).

Specified value: Infinity Ohms

If no wiring faults are found:

- Replace Motronic Engine Control Module (ECM) -J220-.