Oxygen Sensor 2, Checking

Oxygen Sensor 2, Checking

The following procedure is used to diagnose Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) (G131) which is controlled by the Motronic Engine Control Module (ECM) (J623).

• When servicing the electrical harness connector terminals of the 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

• Fuse (SB9) OK.

• 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.

Function test

- Perform the function test located in diagnostic mode 06. => [ Diagnostic Mode 06 - Read Test Results for Specific Diagnostic Functions ] Diagnostic Mode 06 - Read Test Results For Specific Diagnostic Functions.

If specified values are obtained:

- End diagnosis and switch the ignition off.

If the specified values are not obtained:

Test procedure

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

Start diagnosis

- Remove the engine compartment trim.





- Remove the engine cover - 2 -.

- Remove the air filter housing bolts - arrows -.

- Remove the air guide hoses - 1 - and - 6 - from the air filter housing.





- Loosen the hose clamps - 2 - and - 4 - and remove the air filter housing.

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





Checking primary voltage

- Switch the ignition on.

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










Specified value: 1.5 ohms.

If the specification was not obtained:

- Check the wiring for an open circuit, a short circuit to Battery positive (+) or Ground (GND).

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

- If necessary, repair the wiring connection.

If the specification was obtained:

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

- Perform a road test to verify repair.

If the DTC does not return:

Repair complete, Generate readiness code. Refer to => [ Readiness Code ] Readiness Code.

- End diagnosis.

If the DTC returns and no malfunction is found in the wiring and 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 order of the removal, note the following:

Final procedures

After repair work, the following work steps must be performed in the following 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 ] Clearing Diagnostic Trouble Codes.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Readiness Code.

End of Diagnosis