Oxygen Sensor Heaters Before Catalytic Converter, Checking

Oxygen Sensor Heaters before Catalytic Converter, Checking

This procedure is used to check Oxygen Sensor (O2S) Heater (Z19) or Oxygen Sensor (O2S) Heater ( Z28).

• When servicing terminals in harness connector of Heated Oxygen Sensors (HO2S), use only gold-plated terminals.

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test requirements

• The Heated Oxygen Sensor (HO2S) (G39) fuse OK.

• The Heated Oxygen Sensor (HO2S) 2 (G108) fuse 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

- Disconnect the Oxygen Sensor (O2S) Heater (Z19 ) electrical harness connector - 1 -.





To disconnect the Oxygen Sensor (O2S) Heater (-Z28-), perform the following steps:

- Remove the screw - arrow - retaining the coolant reservoir.





- Disconnect the Engine Coolant Level (ECL) Warning Switch (F66) electrical connector from the bottom of the coolant reservoir and set aside the coolant reservoir with the coolant hoses - 1 - and - 2 - connected.

- Disconnect the Oxygen Sensor (O2S) Heater (-Z28- ) electrical harness connector - 2 -.





Checking internal resistance

- Using a multimeter, check the Heated Oxygen Sensor (HO2S) terminals 3 to 5 for resistance.





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

If the specification was not obtained:

- Replace the faulty Heated Oxygen Sensor (HO2S) before the catalytic converter. Refer to Fuel Injection and Ignition Repair Information.

If the specification was obtained:

Checking voltage supply

Switch the ignition on.

- Using a multimeter, check the Heated Oxygen Sensor (HO2S) electrical harness connector terminal 5 to the Engine Component Power Supply Relay (J757) terminal 2/87 for voltage.





Switch the ignition off.

Specified value: Battery voltage.

If the specification was not obtained:

- Check the wiring for a short circuit to each other, Ground (GND), or an open circuit.

- 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 Fuel Injection and Ignition Repair Information.

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

- Remove the Engine Control Module (ECM) (J623 ). Refer to => [ ECM, Removing and Installing ] ECM, Removing and Installing.

- Using a multimeter, check the Oxygen Sensor (O2S) Heater electrical harness connector terminal to the Engine Control Module (ECM) (J623) electrical harness connector T94 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 Engine Control Module (ECM) (J623 ). Refer to => [ ECM, Removing and Installing ] ECM, Removing and Installing.

Assembly is performed in reverse order of removal, note the following:

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 ] Diagnostic Mode 03 - Read DTC Memory.

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

3. If the DTC memory was erased, generate readiness code. => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.

- End of diagnosis.