Oxygen Sensor Heater, Checking

Oxygen Sensor Heater, Checking

NOTE:
- Oxygen Sensor (O2S) Heater Z19 is part of Heated Oxygen Sensor (HO2S) G39 and cannot be replaced separately.
- When servicing terminals in harness connector of Heated Oxygen Sensor (HO2S) G39 , use only gold-plated terminals.

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

Test requirements
- Fuse S344 OK.
- Engine Component Power Supply Relay J757 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







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

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 the Heated Oxygen Sensor (HO2S) G39.

If the specification was obtained:

Checking voltage supply
- Crank the engine (engine may run).







- 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)

- Switch the ignition off.

Specified value: Battery voltage.

If the specification was not obtained:
- Check the Heated Oxygen Sensor (HO2S) G39 electrical harness connector terminal 4 to the Engine Component Power Supply Relay J757 socket 2/87 for an open circuit, a short circuit to each other, Battery (+), or Ground (GND).
- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
- 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 Engine Control Module (ECM) J623.







- Using a multimeter , check the Heated Oxygen Sensor (HO2S) G39 electrical harness connector terminal 3 to the Engine Control Module (ECM) J623 electrical harness connector T94 terminal 51 for resistance.

Heated Oxygen Sensor (HO2S) Engine Control Module (ECM) J623
G39 electrical harness electrical harness 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 an open circuit, a short circuit to each other, Battery (+), or Ground (GND).
- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring and if the voltage supply was OK:
- Erase the DTC memory. Diagnostic Mode 04 - Erase DTC Memory
- 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 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 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