Heated Oxygen Sensor (HO2S) Before Catalytic Converter, Checking

Heated Oxygen Sensor (HO2S) Before Catalytic Converter, Checking

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

NOTE: 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 degrees C.

Function test
Perform a function test of the Heated Oxygen Sensors (HO2S).

If specified values are obtained:
- End diagnosis and switch the ignition off.

If the specified values are not obtained:

Procedure







- 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).

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 Engine Control Module (ECM) J623.







- 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.

Heated Oxygen Sensor (HO2S) Engine Control Module
G39 electrical harness (ECM) J623 electrical
connector terminals connector T94 terminals or test box sockets
1 83
2 61
4 82
6 84

Heated Oxygen Sensor (HO2S) Engine Control Module
-G108- electrical harness (ECM) J623 electrical
connector terminals connector T94 terminals or test box sockets
1 81
2 59
4 60
6 62

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.

Final procedures
After the repair work, the following work steps must be performed in the following sequence:
1. Check the DTC memory.
2. If necessary, erase the DTC memory.
3. If the DTC memory was erased, generate readiness code.

- End of diagnosis.