HO2S After Three Way Catalytic Converter (TWC), Checking

NOTE:
- G130 = O2S behind three way catalytic converter, bank 1
- G131 = O2S behind three way catalytic converter, bank 2
- For functional check of O2S behind three way catalytic converter -G130- or -G131- See Read Measuring value block.


- Disconnect connector for O2S behind three way catalytic converter -G130- or -G131- (component locations refer to "Component Overview - II" Locations ).







- Switch multimeter (Fluke 83 or equivalent) to measure resistance (ohms) and check for continuity between terminal 3 (GND wire) and 4 (signal wire) of heated oxygen sensor.

If continuity is not obtained:
- Replace heated oxygen sensor.

If continuity obtained:







- Switch multimeter (Fluke 83 or equivalent) to 2 volt range and connect between terminals 3 (GND) and 4 (signal wire) on harness connector.
- Switch ignition ON.
Specified value: 400 ± 50 mV

If the specified value is not obtained, check wiring to ECM as follows:
- Switch ignition OFF.
- Connect VAG 1598/19 test box to ECM wiring harness.
- Check following wiring connections for continuity.
Specified value: max. 1 ohms







If the specified value is not obtained:







- Eliminate open or short circuit using wiring diagram.

If wiring OK:
- Replace ECM.

Oxygen sensor heater, checking







NOTE:
- Z29 = Oxygen Sensor (O2S) heater, bank 1
- Z30 = Oxygen Sensor (O2S) heater, bank 2
- For functional check of O2S heater -Z29- or -Z30-.


- Disconnect heated oxygen sensor harness connector (component locations, refer to "Component Overview - II" Locations ).
- Switch multimeter (Fluke 83 or equivalent) to 20 volt range and connect between terminals 1 (B+) and 2 (GND).
- Start engine and let idle.
Specified value: approx. 12 to 14 V

If the specified value is not obtained:
- Check oxygen sensor heater fuse.
- Check fuel pump relay Testing and Inspection
- Check wiring for continuity between terminal 1 and fuse in fuse holder using wiring diagram, if necessary check terminal assignments.
Specified value: max. 1 ohms
- Check wiring for continuity between terminals 2 and 8 on ECM connector E.
Specified value: max. 1 ohms
- Check wiring for continuity between terminals 2 and 3 of ECM connector E (O2S heater -Z30-).
Specified value: max. 1 ohms

If the specified value is obtained:







- Switch multimeter (Fluke 83 or equivalent) to measure resistance (ohms) and connect between terminals 1 and 2.
Specified value (room temperature): approx. 2 to 5 ohms


NOTE: With small increases in temperature, resistance will increase sharply.


If the specified value is not obtained:
- Replace heated oxygen sensor.