Oxygen Sensor 1 after Catalytic Converter, Checking

Oxygen Sensor 1 after Catalytic Converter, Checking

The following procedure is used to diagnose both Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) (G130) and the Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) (G131)

• Vehicle must be raised before the electrical connector of the Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) (G130)and Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) (G131) is accessible.

• When servicing terminals 3 and 4 in the electrical harness connector of the Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) (G130) and Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) (G131), use only gold-plated terminals.

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test requirements

• The Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) (G130)and Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) (G131) fuses Ok.





• Oxygen Sensor (O2S) 1 (behind Three Way Catalytic Converter (TWC)) Heater (Z29) and Oxygen Sensor (O2S) 2 (behind Three Way Catalytic Converter (TWC)) Heater (Z30) OK.

• Battery voltage at least 12.5 volts.

• All electrical consumers such as, lights and rear window defroster, switched off.

• Vehicles with automatic transmission, selector lever in position "P" or "N".

• A/C switched off.

• Ground (GND) connections between engine/transmission/chassis OK.

• Exhaust system between catalytic converter and cylinder head properly sealed.

• Coolant Temperature at least 80° C.

Test procedure

- Perform a preliminary check to verify the customers complaint. Refer to => [ Preliminary Check ] Preliminary Check.

Start diagnosis

Function test

- Connect scan tool.

- Start the engine and let it run at idle.

- Select "Diagnostic mode 6: Check test results of components that are not continuously monitored".

- Select "Test-ID 02: Oxygen sensor monitoring behind catalytic converter".

- Select following Test-IDs.

- Check the specified values at idle.





If the specified values are obtained:

- End diagnosis and switch ignition off.

If the specified values are not obtained:

- Remove the right vehicle floor cover - arrows -.





Checking primary voltage

- Disconnect the brown Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) (G130) electrical harness connector - 1 - or Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) (G131) - 2 -.





- Switch the ignition on.

- Using a multimeter, check the Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) (G130) electrical harness connector terminals 3 to 4 for voltage.





Specified value: 0.400 to 0.500 Volts

- Switch the ignition off.

If the specified value was obtained:

- Replace the Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) (G130) or Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) (G131).

If the specified value was not obtained:

Checking wiring

If the manufacturers test box is being used. Perform the following step.

- Install the test box.

If the manufacturers test box is not being used. Perform the following step.

- Remove the Motronic Engine Control Module (ECM) (J623). Refer to => [ Engine Control Module, Replacing ] Engine Control Module, Replacing.

- Using a Multimeter, check the Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) (G130) electrical harness connector terminals to the Motronic Engine Control Module (ECM) (J623) or Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) (G131) electrical harness connector T94 terminals for an open circuit.













Specified value: 1.5 ohms Max.

If the specification was not obtained:

- Check the wiring for a short circuit to each other, Battery (+), and Ground (GND).

- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

- If necessary, repair the faulty wiring connection.

- Erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

- Perform a road test to verify repair.

If the DTC does not return:

Repair complete, Generate readiness code. Refer to => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.

- End diagnosis.

If the DTC does return and no malfunction is detected in the wiring and the voltage supply was OK:

- Replace the Motronic Engine Control Module (ECM) (J623). Refer to => [ Engine Control Module, Replacing ] Engine Control Module, Replacing.

- Assembly is performed in the reverse of the removal.

Final procedures

After repair work, the following work steps must be performed in the mentioned sequence:

1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Mode 03 - Read DTC Memory.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.