Heated Oxygen Sensor 1 and Sensor Regulation Before Catalytic Converter, Checking

Heated Oxygen Sensor 1 And Sensor Regulation Before Catalytic Converter, Checking

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

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

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

Test requirements
- The Motronic Engine Control Module (ECM) J623 fuses OK.
- The Oxygen Sensor (O2S) Heater Z19 before catalytic converter 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 the function test located in diagnostic mode 06.

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. General Diagnosis

Start diagnosis
- Raise the vehicle.







- Disconnect the black Heated Oxygen Sensor (HO2S) G39 electrical harness connector - 2 -.

Checking primary voltage
- Crank the engine.







- Using a multimeter , check the Heated Oxygen Sensor (HO2S) G39 electrical harness connector terminals 6 to 5 for voltage.

Specified value: 0.400 to 0.500 Volts

- Switch the ignition off.

If the specified value was not obtained:
- Replace Heated Oxygen Sensor (HO2S) G39.

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 electrical harness connector terminals to the Motronic Engine Control Module (ECM) J623 electrical harness connector T94 terminals for an open circuit.

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

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, lose or broken terminals.
- If necessary, repair the faulty wiring connection.

If no malfunction is found in the wiring:
- Replace the Motronic Engine Control Module (ECM) J623.

Final procedures
After repair work, the following work steps must be performed in the following sequence:
1. Check the DTC memory. Diagnostic Mode 03 - Read DTC Memory
2. If necessary, erase the DTC memory. Diagnostic Mode 04 - Erase DTC Memory
3. If the DTC memory was erased, generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

- End of diagnosis.