Heated Oxygen Sensors Before Catalytic Converter, Checking

Heated Oxygen Sensors before Catalytic Converter, Checking

This procedure is used to diagnose Heated Oxygen Sensor (HO2S) (G39) or Heated Oxygen Sensor (HO2S) 2 (G108).

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

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test requirements

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

• The Heated Oxygen Sensor (HO2S) 2 (G108) fuse OK.

• 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.

Function test

Perform a function test of the Heated Oxygen Sensors (HO2S). Refer to ADD LINK

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 => [ General Diagnosis ] General Diagnosis.

Start diagnosis

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





To disconnect the Heated Oxygen Sensor (HO2S) 2 (G108), perform the following steps:

- Remove the screw - arrow - retaining the coolant reservoir.





- Disconnect the Engine Coolant Level (ECL) Warning Switch (F66) electrical connector from the bottom of the coolant reservoir and set aside the coolant reservoir with the coolant hoses - 1 - and - 2 - connected.

- Disconnect the Oxygen Sensor (O2S) Heater (-Z28- ) electrical harness connector - 2 -.





Checking primary voltage

- Using a multimeter, check the Heated Oxygen Sensor (HO2S) electrical harness connector terminals 1 to 2 for voltage.





Specified value: 0.400 to 0.500 Volts

- Switch the ignition off.

If the specified value was obtained:

- Replace the faulty Heated Oxygen Sensor (HO2S). Refer to Fuel Injection and Ignition Repair Information.

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. Refer to Fuel Injection and Ignition Repair Information.

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

- Remove the Engine Control Module (ECM) (J623 ). Refer to => [ ECM, Removing and Installing ] ECM, Removing and Installing.

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













Specified value: 1.5 ohms Max.

If any of the specified values are not obtained:

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

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

- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring:

- Replace the Engine Control Module (ECM) (J623 ). Refer to => [ ECM, Removing and Installing ] ECM, 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. => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Mode 03 - Read DTC Memory.

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

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

- End of diagnosis.