Oxygen Sensor 1 Heater, Checking

Oxygen Sensor 1 Heater, Checking

The following procedure is used to diagnose Oxygen Sensor (O2S) Heater Z19 for Heated Oxygen Sensor (HO2S) G39 which is controlled by the Motronic Engine Control Module (ECM) J623.

NOTE: When servicing electrical harness connector terminals for the Heated Oxygen Sensors , use only gold- plated terminals.

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

Test requirements
- Heated Oxygen Sensor (HO2S) Circuit Breaker S73 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 (GND) connections between engine/transmission/chassis OK.
- Ignition switched off.

Test procedure
- Perform a preliminary check to verify the customers complaint. General Diagnosis

Start diagnosis
- Raise the vehicle.







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

Checking internal resistance







- Using a multimeter , check the Heated Oxygen Sensor (HO2S) G39 terminals 3 to 4 for resistance.

Specified value: 2.5 to 10.0 Ohms (at approx. 20 degrees C)

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

If the specification was obtained:

Checking voltage supply
- Crank the engine.







- Using a multimeter , check the Heated Oxygen Sensor (HO2S) G39 electrical harness connector terminal 4 to Ground (GND) for voltage.

Heated Oxygen Sensor (HO2S) Measure to
G39 electrical harness
connector terminal
4 Ground(GND)

Specified value: Battery voltage.

- Switch the ignition off.

If the specification was not obtained:
- Check the electrical harness connector for damage, corrosion, lose or broken terminals.
- Check the wiring from the Heated Oxygen Sensor (HO2S) G39 electrical harness connector terminal 4 to the Engine Component Power Supply Relay J757 socket 2/87 for a short circuit to each other, Ground (GND), or an open circuit.
- If necessary, repair the faulty wiring connection.

If the specification 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.







- Using a multimeter , check the Heated Oxygen Sensor (HO2S) G39 electrical harness connector to the Motronic Engine Control Module (ECM) J623 electrical harness connector T94 for an open circuit.

Heated Oxygen Sensor (HO2S) Motronic Engine Control Module
G39 electrical harness (ECM) J623 electrical connector T94
connector terminal terminal or test box socket
3 51

Specified value: 1.5 Ohms max.

If the specification was not obtained:
- Check the wiring for a short circuit to each other, Battery (+), Ground (GND) or an open circuit.
- 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.

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.