Oxygen Sensor Before Catalytic Converter, Checking Function

Diagnostic Procedures

Oxygen Sensor Heater Before Catalytic Converter, Checking

Oxygen Sensor 1 Heater

The following procedure is used to diagnose Oxygen Sensor (O2S) Heater (Z19) for Heated Oxygen Sensor (HO2S) (G39) which is controlled by the Motronic Engine Control Module (ECM) (J623).

• When servicing electrical harness connector terminals for the Heated Oxygen Sensors, use only gold-plated terminals.

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test requirements

• Fuse (SC6) OK.

• Battery voltage at least 12.5 volts.

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

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

• A/C switched off.

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

• Ignition switched off.

Procedure

- Raise the vehicle.

- Loosen the quick release fasteners - 1 - and - 2 - and remove the noise insulation panel.





- Disconnect the black Heated Oxygen Sensor (HO2S) (G39) electrical harness connector - 3 -.





Checking internal resistance

- Using a multimeter, check the Heated Oxygen Sensor (HO2S) (G39) terminals 3 to 4 for resistance.





Specified value: 2.5 to 10.0 ohms (at approx. 20 °C)

If the specification was not obtained:

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

If the specification was obtained:

Checking voltage supply

Crank the engine.

- Using a multimeter, check the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector terminal 4 to Ground (GND) for voltage.









Specified value: Battery voltage.

Switch the ignition off.

If the specification was not obtained:

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

- Check the wiring from the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector terminal 4 to the Engine Component Power Supply Relay (J757) socket 2/87 for a short circuit to each other, Ground (GND), or an open circuit.

- If necessary, repair the faulty wiring connection.

If the specification was obtained:

Checking Ground (GND) activation

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).

- Using a multimeter, check the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector to the Motronic Engine Control Module (ECM) (J623) electrical harness connector T94a 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 (+), Ground (GND) or an open circuit.

- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring and if the voltage supply was OK:

- Replace the Motronic Engine Control Module (ECM) (J623).

Assembly is performed in the reverse order of removal.

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 Modes 01 - 09.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.

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

- End of diagnosis.

Oxygen Sensor 2 Heater

The following procedure is used to diagnose Oxygen Sensor (O2S) 2 Heater (Z28) for Heated Oxygen Sensor (HO2S) 2 (G108) which is controlled by the Motronic Engine Control Module (ECM) (J623).

• When servicing electrical harness connector terminals for the Heated Oxygen Sensors, use only gold-plated terminals.

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test requirements

• Fuse (SC6) OK.

• Battery voltage at least 12.5 volts.

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

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

• A/C switched off.

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

• Ignition switched off.

Procedure

- Raise the vehicle.

- Loosen the quick release fasteners - 1 - and - 2 - and remove the noise insulation panel.





- Disconnect the black Heated Oxygen Sensor (HO2S) 2 (G108) electrical harness connector- 1 -.





Checking internal resistance

- Using a multimeter, check the Heated Oxygen Sensor (HO2S) 2 (G108) terminals 3 to 4 for resistance.





Specified value: 2.5 to 10.0 ohms (at approx. 20 °C)

If the specification was not obtained:

- Replace Heated Oxygen Sensor (HO2S) 2 (G108).

If the specification was obtained:

Checking voltage supply

Crank the engine.

- Using a multimeter, check the Heated Oxygen Sensor (HO2S) 2 (G108) electrical harness connector terminal 4 to Ground (GND) for voltage.









Specified value: Battery voltage.

Switch the ignition off.

If the specification was not obtained:

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

- Check the wiring from the Heated Oxygen Sensor (HO2S) 2 (G108) electrical harness connector terminal 4 to the Engine Component Power Supply Relay (J757) socket 2/87 for a short circuit to each other, Ground (GND), or an open circuit.

- If necessary, repair the faulty wiring connection.

If the specification was obtained:

Checking Ground (GND) activation

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).

- Using a multimeter, check the Heated Oxygen Sensor (HO2S) 2 (G108) electrical harness connector to the Motronic Engine Control Module (ECM) (J623) electrical harness connector T94a 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 (+), Ground (GND) or an open circuit.

- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring and if the voltage supply was OK:

- Replace the Motronic Engine Control Module (ECM) (J623).

- Assembly is performed in the reverse order of removal.

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 Modes 01 - 09.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.

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

- End of diagnosis.

Oxygen Sensor 3 Heater

The following procedure is used to diagnose Oxygen Sensor (O2S) 3 Heater (Z62) for Heated Oxygen Sensor (HO2S) 3 (G285) which is controlled by theEngine Control Module (ECM) 2 (J624).

• When servicing electrical harness connector terminals for the Heated Oxygen Sensors, use only gold-plated terminals.

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test requirements

• Fuse (SC6) OK.

• Battery voltage at least 12.5 volts.

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

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

• A/C switched off.

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

• Ignition switched off.

Procedure

- Raise the vehicle.

- Loosen the quick release fasteners - 1 - and - 2 - and remove the noise insulation panel.





- Disconnect the brown Heated Oxygen Sensor (HO2S) 3 (G285) electrical harness connector - 2 -.





Checking internal resistance

- Using a multimeter, check the Heated Oxygen Sensor (HO2S) 3 (G285) terminals 3 to 4 for resistance.





Specified value: 2.5 to 10.0 ohms (at approx. 20 °C)

If the specification was not obtained:

- Replace Heated Oxygen Sensor (HO2S) 3 (G285).

If the specification was obtained:

Checking voltage supply

Crank the engine.

- Using a multimeter, check the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector terminal 4 to Ground (GND) for voltage.









Specified value: Battery voltage.

Switch the ignition off.

If the specification was not obtained:

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

- Check the wiring from the Heated Oxygen Sensor (HO2S) 3 (G285) electrical harness connector terminal 4 to the Engine Component Power Supply Relay (J757) socket 2/87 for a short circuit to each other, Ground (GND), or an open circuit.

- If necessary, repair the faulty wiring connection.

If the specification was obtained:

Checking Ground (GND) activation

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 Engine Control Module (ECM) 2 (J624).

- Using a multimeter, check the Heated Oxygen Sensor (HO2S) 3 (G285) electrical harness connector to the Engine Control Module (ECM) 2 (J624) electrical harness connector T94d 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 (+), Ground (GND) or an open circuit.

- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring and if the voltage supply was OK:

- Replace the Engine Control Module (ECM) 2 (J624).

- Assembly is performed in the reverse order of removal.

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 Modes 01 - 09.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.

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

- End of diagnosis.

Oxygen Sensor 4 Heater

The following procedure is used to diagnose Oxygen Sensor (O2S) 4 Heater (Z63) for Heated Oxygen Sensor (HO2S) 4 (G286) which is controlled by theEngine Control Module (ECM) 2 (J624).

• When servicing electrical harness connector terminals for the Heated Oxygen Sensors, use only gold-plated terminals.

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test requirements

• Fuse (SC6) OK.

• Battery voltage at least 12.5 volts.

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

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

• A/C switched off.

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

• Ignition switched off.

Procedure

- Raise the vehicle.

- Loosen the quick release fasteners - 1 - and - 2 - and remove the noise insulation panel.





- Disconnect the brown Heated Oxygen Sensor (HO2S) 4 (G286) electrical harness connector- 2 -.





Checking internal resistance

- Using a multimeter, check the Heated Oxygen Sensor (HO2S) 4 (G286) terminals 3 to 4 for resistance.





Specified value: 2.5 to 10.0 ohms (at approx. 20 °C)

If the specification was not obtained:

- Replace Heated Oxygen Sensor (HO2S) 4 (G286).

If the specification was obtained:

Checking voltage supply

Crank the engine.

- Using a multimeter, check the Heated Oxygen Sensor (HO2S) 4 (G286) electrical harness connector terminal 4 to Ground (GND) for voltage.









Specified value: Battery voltage.

Switch the ignition off.

If the specification was not obtained:

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

- Check the wiring from the Heated Oxygen Sensor (HO2S) 4 (G286) electrical harness connector terminal 4 to the Engine Component Power Supply Relay (J757) socket 2/87 for a short circuit to each other, Ground (GND), or an open circuit.

- If necessary, repair the faulty wiring connection.

If the specification was obtained:

Checking Ground (GND) activation

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 Engine Control Module (ECM) 2 (J624).

- Using a multimeter, check the Heated Oxygen Sensor (HO2S) 4 (G286) electrical harness connector to the Engine Control Module (ECM) 2 (J624) electrical harness connector T94d 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 (+), Ground (GND) or an open circuit.

- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring and if the voltage supply was OK:

- Replace the Engine Control Module (ECM) 2 (J624).

- Assembly is performed in the reverse order of removal.

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 Modes 01 - 09.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.

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

- End of diagnosis.