Heated Oxygen Sensor, Checking

Heated Oxygen Sensor, Checking

• Use only gold-plated terminals when servicing terminals in the electrical harness connector of the Heated Oxygen Sensor (HO2S) (G39 ).

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test requirements

• The Heated Oxygen Sensor (HO2S) (G39) fuse OK.

• The Oxygen Sensor (O2S) Heater (Z19) before catalytic converter OK. Refer to=> [ Heated Oxygen Sensor before Catalytic Converter, Checking Heater ] Heated Oxygen Sensor Before Catalytic Converter, Checking Heater.

• Battery voltage at least 12.5 volts.

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

• 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.

Function test

- Perform the function test in diagnostic Mode 6. Refer to => [ Diagnostic Mode 06 - Read Test Results for Specific Diagnostic Functions ] Diagnostic Mode 06 - Read Test Results for Specific Diagnostic Functions.

If the specified values are not obtained:

Checking primary voltage

- Disconnect the black Heated Oxygen Sensor (HO2S) (G39) electrical harness connector - 1 -.





- Using a multimeter, check the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector - 1 - terminals 1 to 5 for voltage.





Specified value: 0.400 to 0.500 Volts

- Switch the ignition off.

If the specified value was obtained:

- Replace the Heated Oxygen Sensor (HO2S) (G39).

If the specified value is obtained:

Checking wiring

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

- Install the Test Box 105 Pin (VAG1598/42).

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, Removing and Installing ] Engine Control Module, Removing and Installing.

- Using a Multimeter, check the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector terminals to the Motronic Engine Control Module (ECM) ( J623) electrical harness connector T94 terminals for resistance.









Specified value: 1.5 ohms Max.

If the specification was not obtained:

- Check the wiring for an open circuit, 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.

If no malfunction is detected in the wiring:

- 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 ] Readiness Code.

- End of 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, Removing and Installing ] Engine Control Module, Removing and Installing.

Final procedures

After the 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 ] Diagnostic Mode 04 - Erase DTC Memory.

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