Heated Oxygen Sensor G39, Checking

Heated Oxygen Sensor G39, Checking

The following procedure is used to diagnose both Heated Oxygen Sensor (HO2S) G39 and Heated Oxygen Sensor (HO2S) 2 G108

NOTE: Use only gold-plated terminals when servicing terminals in the electrical harness connectors of the Heated Oxygen Sensor (HO2S) G39 and Heated Oxygen Sensor (HO2S) 2 G108.

Special tools, testers and auxiliary items required
- Multimeter.
- Wiring diagram.

Test requirements







- The Heated Oxygen Sensor (HO2S) G39 and Oxygen Sensor (O2S) 2 Heater Z28 fuses OK.
- The Oxygen Sensor (O2S) Heater Z19 and Oxygen Sensor (O2S) 2 Heater Z28 before catalytic converter OK. Refer to.
- 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.

Test procedure
- Perform a preliminary check to verify the customers complaint. Preliminary Check

Function test
- Perform the function test in Diagnostic Mode 06. Diagnostic Mode 06 - Read Test Results For Specific Diagnostic Functions
- End diagnosis and switch the ignition off.

If the specified values are not obtained:

Start Diagnosis







- Disconnect the Heated Oxygen Sensor (HO2S) G39 electrical harness connector - 2 - or the Heated Oxygen Sensor (HO2S) 2 G108 - 4 -.

Checking primary voltage







- 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 not obtained:
- Replace the Heated Oxygen Sensor (HO2S) G39 or the Heated Oxygen Sensor (HO2S) 2 G108.

If the specified value was 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 Motronic Engine Control Module (ECM) J623.







- Using a Multimeter, check the Heated Oxygen Sensor (HO2S) G39 or the Heated Oxygen Sensor (HO2S) 2 G108 electrical harness connector terminals to the Motronic Engine Control Module (ECM) J220 electrical harness connector T121 terminals for an open circuit.

Heated Oxygen Sensor (HO2S) Motronic Engine Control Module
G39 electrical harness (ECM) J623 electrical connector
connector terminals T94 terminals or test box sockets
1 60
2 61
3 51
5 81
6 82

Heated Oxygen Sensor (HO2S) Motronic Engine Control Module
2 G108 electrical harness (ECM) J623 electrical connector
connector terminals T94 terminals or test box sockets
1 59
2 84
3 73
5 83
6 62

Specified value: 1.5 Ohms Max.

If the specification was not obtained:
- Check the wiring for a 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.
- Erase the DTC memory. Diagnostic Modes 01 - 09.
- Perform a road test to verify repair.

If the DTC does not return:
Repair complete, Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
- End 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.
- Assembly is performed in the reverse of the removal.

Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:

1. Check the DTC memory. Diagnostic Modes 01 - 09
2. If necessary, erase the DTC memory. Diagnostic Modes 01 - 09
3. If the DTC memory was erased, generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

End of Diagnosis