Oxygen Sensor Heaters Before and After Converter, Checking

Oxygen Sensor Heater For Oxygen Sensors Before And Behind Three Way Catalytic Converter (TWC), Checking

Checking voltage supply for oxygen sensor heating

NOTE: When servicing terminals in harness connector of Heated Oxygen Sensor (HO2S), use only goldplated terminals.

Recommended special tools and equipment
- VAG1526 multimeter or VAG1715 multimeter
- VAG1594 connector test kit
- Wiring diagram

Test requirements







- The respective fuses of oxygen sensors must be OK:
Component locations of 4-pin harness connectors for oxygen sensors.
- Disconnect 4-pin harness connector to the respective oxygen sensor.







- Use adapter cables from V.A.G 1594 to connect multimeter to sockets 1 (B+) and 2 (Ground -GND-) for voltage measurement.

Connector assignment for engines with engine code "BEL".
- Operate starter briefly.
Specified value: approx.. battery voltage

If there is no voltage:
- Use adapter cables from V.A.G 1594 to connect multimeter to socket 1 (B+) and vehicle Ground (GND) for voltage measurement.







- Assignment of connector sockets at wiring harness for vehicles with engine code "BEL".







- Assignment of connector sockets at oxygen sensor for vehicles with engine code "BEL".
- Operate starter briefly.
Specified value: approx.. battery voltage

If there is no voltage again:
- Check wire connection of socket 1 of the respective oxygen sensor connector at wiring harness via Fuel Pump (FP) relay for open circuit and short circuit according to wiring diagram.

If voltage supply is OK.







- Use adapter cables from V.A.G 1594 to connect multimeter to socket 2 (Ground -GND- activation of Engine Control Module) and B+.
- Start engine.
Specified value: approx. battery voltage, fluctuating.

NOTE: At certain operating points, the ECM "pulses" the Ground (GND) for oxygen sensor heating. This means that the Ground (GND) is constantly switched on and off at these points. It is therefore possible that the voltage displayed on the tester will fluctuate.

- Switch ignition off.

If there is no voltage:
- Connect test box to control module wiring harness, connect test box for wiring test. Test Box, Connecting For Wiring Test







- Check the following wire connection for open circuit:

Oxygen sensor before catalytic converter: Bank 1 Heated Oxygen Sensor (HO2S) -G39-

Connector at wiring VAG1598/31 test
harness socket box, socket
2 5 (Ground -GND-)

Oxygen sensor before catalytic converter: Bank 2 Heated Oxygen Sensor (HO2S) 2 - G108-

Connector at wiring VAG1598/31 test
harness socket box, socket
2 4 (Ground -GND-)

Oxygen sensor behind catalytic converter: Bank 1 Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130-

Connector at wiring VAG1598/31 test
harness socket box, socket
2 63 (Ground -GND-)

Oxygen sensor behind catalytic converter: Bank 2 Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) -G131-

Connector at wiring VAG1598/31 test
harness socket box, socket
2 6 (Ground -GND-)

Wire resistance: max: 1.5 Ohm

If wire connections are OK.
- Replace appropriate Oxygen Sensor (O2S).
- Read readiness code. If DTC memory was erased, readiness code must be re-generated.
Read Readiness Code
Readiness Code, Generating