Oxygen Sensor Heaters, Checking

Oxygen Sensor Heaters, Checking

The following procedure is used to diagnose Oxygen Sensor (O2S) Heater (Z19) for Heated Oxygen Sensor (HO2S) (G39) and Oxygen Sensor (O2S) 2 Heater (Z28) for Heated Oxygen Sensor (HO2S) 2 (G108).

• When servicing electrical harness connector terminals for the Heated Oxygen Sensor (HO2S) (G39), use only gold-plated terminals.

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test requirements

• The Oxygen Sensor (O2S) Heater (Z19) for Heated Oxygen Sensor (HO2S) (G39) and Oxygen Sensor (O2S) 2 Heater (Z28) for Heated Oxygen Sensor (HO2S) 2 (G108) fuses 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. Refer to => [ General Diagnosis ] General Diagnosis.

Start diagnosis

- Remove the engine cover with air filter.

Checking internal resistance

- Disconnect the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector - 2 - or the Heated Oxygen Sensor (HO2S) 2 (G108) electrical harness connector- 1 -.





- Using a multimeter, check the Heated Oxygen Sensor (HO2S) terminals 3 to 4 for an open circuit.

Specified value: 2.5 to 10.0 ohms (at approx. 20° C)

If the specification was not obtained:

- Replace the 2- Heated Oxygen Sensor (HO2S) (G39) or the 1- Heated Oxygen Sensor (HO2S) 2 (G108).

If the specification was obtained:

Checking voltage supply

- Using a multimeter, check the Heated Oxygen Sensor (HO2S) electrical harness connector terminal 4 to the Fuel Pump (FP) 2 Relay (J49) terminal 2/87 for voltage.










Specified value: Battery voltage.

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 the specification was obtained:

Checking Ground (GND) activation

If the manufacturers test box is being used. Perform the following step.

- Install the test box. Refer to repair information.

If the manufacturers test box is not being used. Perform the following step.

- Remove the Motronic Engine Control Module (ECM) (J220). Refer to => [ Motronic Engine Control Module, Replacing ] Motronic Engine Control Module, Replacing.

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











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 detected in the wiring and if the voltage supply was OK:

- Replace the Motronic Engine Control Module (ECM) (J220). Refer to => [ Motronic Engine Control Module, Replacing ] Motronic Engine Control Module, Replacing.

- Install the engine cover with air filter.

Final procedures

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

1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Mode 03 - Read DTC Memory.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Readiness Code.

- End of diagnosis.