Oxygen Sensors Before Catalytic Converter, Checking Heating

Oxygen Sensors Before Catalytic Converter, Checking Heating







Special tools and equipment
- VAG1526 A
- VAG1594 A
- VAG1598/31

Test requirements
- Fuse for oxygen sensor heating OK

Test sequence
- Disconnect 6-pin connector of bank 1, Heated Oxygen Sensor (HO2S) -G39-.







- 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.
- Start engine.
- Specified value: approx. battery voltage

NOTE: 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.

If no voltage is present:







- Connect multimeter as follows to measure voltage.

Connector terminal Measure to
3 Engine ground

- 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:

If voltage supply is OK:







- Connect multimeter as follows to measure voltage:

Connector Measure to
terminal
4 (Ground actuation by engine Battery positive
control module)

- Start engine.
- Specified value: approx. battery voltage

NOTE: 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.







- Check for open circuit in following wiring connections:

Connector Test box VAG1598/31
terminal Socket
4 5

- Repair open circuit, if necessary.

If wiring is OK but there is no Ground supply for the oxygen sensor heating:
- Replace engine control module.