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Oxygen Sensor 2 Heater, Checking



Oxygen Sensor 2 Heater, Checking

The following procedure is used to diagnose Oxygen Sensor (O2S) 2 Heater Z28 for Heated Oxygen Sensor (HO2S) 2 G108 which is controlled by the Engine Control Module (ECM) 2 J624.

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) 2 G108 electrical harness connector - 4 -.

Checking internal resistance







- Using a multimeter , check the Heated Oxygen Sensor (HO2S) 2 G108 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) 2 G108.

If the specification was obtained:

Checking voltage supply
- Crank the engine.







- Using a multimeter , check the Heated Oxygen Sensor (HO2S) 2 G108 electrical harness connector terminal 4 to Ground (GND) for voltage.

Heated Oxygen Sensor (HO2S) 2 Measure to
G108 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) 2 G108 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 Engine Control Module (ECM) 2 J624.







- Using a multimeter , check the Heated Oxygen Sensor (HO2S) 2 G108 electrical harness connector to the Engine Control Module (ECM) 2 J624 electrical harness connector T94a for an open circuit.

Heated Oxygen Sensor (HO2S) Engine Control Module (ECM) 2
2 G108 electrical harness J624 electrical connector T94a
connector terminal terminal or test box socket

4 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 Engine Control Module (ECM) 2 J624.

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.