Oxygen Sensors After Catalytic Converter, Checking Heating

Oxygen Sensors after Catalytic Converter, Checking Heating

Special tools, testers and auxiliary items required

• (VAG1526A)

• (VAG1594A)

• (VAG1598/31)

Test requirements

• Fuse for oxygen sensor heating OK.

Test sequence

- Disconnect 4-pin connector of relevant oxygen sensor behind catalytic converter => [ Identification of connector bracket - right
side of vehicle ] Locations or => [ Identification of connector bracket - left side
of vehicle ] Locations

- Connect multimeter between terminals 1 and 2 to measure resistance.





• Specified value at room temperature 6.4 to 47.5 ohms

If specified value is not obtained:

- Replace relevant oxygen sensor behind catalytic converter.

If specified value is obtained:

Check voltage supply for oxygen sensor heating

- Connect multimeter between terminals 1 (positive) and 2 (Ground) 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 4.

If no voltage is present:

- Connect multimeter as follows to measure voltage:









- Operate starter briefly.

• Specified value: approx. battery voltage

If no voltage is present:

- Check wiring from terminal 1 on connector via fuse to fuel pump relay for an open circuit.

If voltage supply is OK:

- Connect multimeter as follows to measure voltage:









- Start engine.

• Specified value: approx. battery voltage, may fluctuate

- 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:





• Oxygen sensor (O2S) heater 1 (Z29) Bank 1 behind Cat:





• Oxygen Sensor (O2S) heater 2 (Z30) Bank 2 behind Cat:





- Repair open circuit, if necessary.

If wiring is OK but there is no Ground (GND) supply for oxygen sensor heater:

- 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.