Oxygen Sensor Heater After Catalytic Converter, Checking

Oxygen Sensor Heater after Catalytic Converter, Checking

Special tools, testers and auxiliary items required

• Multimeter (V.A.G 1526 A)

• Connector test kit (V.A.G 1594 A)

• Text box (VAG1598/31)

Requirements

• Coolant temperature at least 80 °C.

• Fuse for Oxygen Sensor (O2S) heating OK.



Work sequence

- Disconnect 4-pin connector - 2 - (brown) to Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) (G130).





• To gain access to the connector, remove coolant expansion tank bolt (arrow) and move expansion tank to side. Fuel hoses remain connected.





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

If specified value is obtained:

- Connect multimeter between terminals - 1 - (B+) and - 2 - (Ground) to measure voltage.





- Start engine.

• Specified value: approx. battery voltage (B+)

• Points at which Oxygen Sensor (O2S) heating is switched on and off by the ECM can be observed in "Reading measured value block" function, display group number 041 and display field 4.

If no voltage is present:

- Connect multimeter as follows to measure voltage:









- Operate starter briefly.

• Specified value: approx. battery voltage (B+)

If no voltage is present again:

- Check wire connection from connector terminal 1 via fuse to fuel pump relay for open circuit. Refer to

If voltage supply is OK:

- Connect multimeter as follows to measure voltage:









- Start engine.

• Specified value: approx. battery voltage (B+), voltage may fluctuate

If no voltage is present:

- Connect test box (VAG1598/31) to wiring harness for ECM; do not connect to ECM. Refer to => [ Electrical Testing, with Test Box VAG 1598/31 ] Electrical Testing, With Test Box VAG 1598/31.

- Check for open circuit in the following wiring connections:









- Repair open circuit, if necessary.

If wiring is OK but there is no ground (GND) supply for the Oxygen Sensor (O2S) heating:

- Replace ECM. Refer to => [ Engine Control Module without Metal Anti-Theft Housing, Replacing ] Engine Control Module Without Metal Anti-Theft Housing, Replacing.