Oxygen Sensor Heater In Center Three Way Catalytic Converter , Checking

Diagnostic Procedures

Oxygen Sensor Heater in center Three Way Catalytic Converter , Checking

• When servicing terminals in harness connector of Heated Oxygen Sensor (HO2S) (G465), use only gold-plated terminals.

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

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Test requirements

• The Heated Oxygen Sensor (HO2S) (G465) fuse 21 in Fuse Panel B is 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 connections between engine/transmission/chassis OK.

• Ignition switched off.

Test procedure

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

Start diagnosis

- Remove the engine cover with air filter. Refer to the repair information.

Checking internal resistance

- Disconnect the Heated Oxygen Sensor (HO2S) (G465 ) electrical harness connector.





- Using a multimeter, check the Heated Oxygen Sensor (HO2S) (G465) terminals 1 and 2 for correct resistance.





Specified value: 2.5 to 14.0 ohms (at approx. 20 °C)

If the specified value was Not obtained:

- Replace the Heated Oxygen Sensor (HO2S) (G465 ). Refer to the repair information.

If the specified value was obtained:

Checking voltage supply

- Turn the ignition switch ON

- Using a multimeter, check the Heated Oxygen Sensor (HO2S) (G465) electrical harness connector terminal 1 to engine ground for voltage.





Specified value: Battery voltage.

- Turn the ignition switch OFF

If the specified value was Not obtained:

- Check the wiring for an open, high resistance or short to Ground and replace any open fuse.

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

- If necessary, repair the faulty wiring connection.

If the specified value 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). Refer to the repair information.

- Using a multimeter, check the Heated Oxygen Sensor (HO2S) (G465) electrical harness connector terminal to the Motronic Engine Control Module (ECM) (J623) electrical harness connector T94 for an open circuit.





Specified value: 1.5 ohms max.

If the specified value was Not obtained:

- Check the wiring for an open or high resistance.

- 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 and if the voltage supply was OK:

- Replace the Motronic Engine Control Module (ECM) (J623). Refer to the repair information.

- Install the engine cover with air filter. Refer to the repair information.

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 ] Scan Tool Testing and Procedures.

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

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