Oxygen Sensors Before Catalytic Converter, Checking Heating

Oxygen Sensors before Catalytic Converter, Checking Heating

Special tools, testers and auxiliary items required

• (VAG1526A)

• (VAG1594A)

• (VAG1598/31)

Test requirements

• Fuse for oxygen sensor heating OK. Refer to

Test sequence

- Disconnect 6-pin connector of bank 1, Heated Oxygen Sensor (HO2S) (G39) => [ Identification of connector bracket - right
side of vehicle ] Locations

- Connect multimeter between terminals 3 and 4 to measure resistance.

• Specified value at room temperature 2.5 to 10 ohms

If specified value is not obtained:

- Replace HO2S (G39).

If specified value is obtained:

Check voltage supply for oxygen sensor heating

- Connect multimeter between terminals 3 and 4 to measure voltage.

- Operate starter briefly.

• Specified value: approx. battery voltage

If no voltage is present:

- Check wiring from terminal 3 on connector via fuse to fuel pump relay for an open circuit. Refer to

If voltage supply is OK:

- Connect multimeter as follows to measure voltage:

- Start engine.

• Specified value: approx. battery voltage

• Points at which oxygen sensor heating is switched on and off by engine control module can be observed in "Reading measured value block" function, display group number 041 and display zone 2.

- Switch ignition off.

If no voltage is present:

- Connect test box (VAG1598/31) to wiring harness for engine control module; do not connect engine control module. Refer to => [ Wiring and Component Check with Test Box VAG 1598/31 ] Wiring and Component Check With Test Box VAG 1598/31.

- Check for open circuit in following wiring connections:

- Repair open circuit, if necessary.

If wiring is OK but there is no Ground supply for the oxygen sensor heating:

- Replace engine control module:

• With anti-theft housing. Refer to => [ Engine Control Module with Metal Anti-Theft Housing ] Engine Control Module With Metal Anti-Theft Housing.

• Without anti-theft housing. Refer to => [ Engine Control Module without Metal Anti-Theft Housing ] Engine Control Module Without Metal Anti-Theft Housing.