Malibu, Malibu MAXX 2006-2008

Heated Oxygen Sensor

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Operation



Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The engine control module (ECM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started, the ECM operates in Open Loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and Closed Loop is achieved, the HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream. Low HO2S voltage indicates a lean exhaust stream.

Removal & Installation



2.2L (L61) Engine
Front Sensor 1

WARNING
The in-line connector and louvered end must be kept clear of grease, dirt or other contaminants. Avoid using cleaning solvents of any type. DO NOT drop or roughly handle the heated oxygen sensor (HO2S).

  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Remove the Connector Position Assurance (CPA) retainer.
  4.  
  5. Disconnect the engine wiring harness electrical connector from the HO2S electrical connector.
  6.  
  7. Remove the HO2S electrical connector rosebud clip from the thermostat housing tab.
  8.  
  9. Remove the HO2S.
    NOTE
    A special anti-seize compound is used on the HO2S threads. The compound consists of a liquid graphite and glass beads. The graphite will burn away, but the glass beads will remain, making the sensor easier to remove. New or service sensors will have the compound applied to the threads. If a sensor is removed and is to be reinstalled, the threads must have an anti-seize compound applied before installation.

  10.  

To install:

  1. If reinstalling the old HO2S, coat the threads with anti-seize compound.
  2.  
  3. Install the HO2S and tighten to 31 ft. lbs. (42 Nm).
  4.  
  5. Connect the engine wiring harness electrical connector to the HO2S electrical connector.
  6.  
  7. Install the CPA retainer.
  8.  
  9. Install the HO2S electrical connector rosebud clip to the thermostat housing tab.
  10.  

Rear Sensor 2

NOTE
The HO2S may be difficult to remove when the engine temperature is less than 48°C (120°F).

  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Raise and support the vehicle.
  4.  
  5. Remove the Connector Position Assurance (CPA) retainer.
  6.  
  7. Disconnect the engine wiring harness electrical connector from the HO2S electrical connector.
  8.  
  9. Using the J 39194, remove the HO2S.
  10.  

To install:


NOTE
A special anti-seize compound is used on the HO2S threads. The compound consists of a liquid graphite and glass beads. The graphite will burn away but the glass beads will remain, making the sensor easier to remove. New or service sensors already have the compound applied to the threads. If the sensor is removed and is to be reinstalled, the threads must be coated with an anti-seize compound before reinstallation.

  1. If reinstalling the old HO2S, coat the threads with anti-seize compound.
  2.  
  3. Using the J 39194, install the HO2S. Tighten to 31 ft. lbs. (42 Nm).
  4.  
  5. Connect the engine wiring harness electrical connector (2) to the HO2S electrical connector.
  6.  
  7. Install the CPA retainer.
  8.  
  9. Lower the vehicle.
  10.  

3.5L (LZ4) & 3.9L (LZ9) Engines
Bank 1 Sensor 1
  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Remove the intake manifold cover.
  4.  
  5. Remove the Connector Position Assurance (CPA) retainer.
  6.  
  7. Disconnect the engine wiring harness electrical connector from the heated oxygen sensor (HO2S) electrical connector.
  8.  
  9. Remove the HO2S electrical connector rosebud clip from the ignition coil bracket.
    NOTE
    The oxygen sensor may be difficult to remove when the engine temperature is below 48°C (120°F). Excessive force may damage threads in the exhaust manifold or the exhaust pipe.

  10.  
  11. Remove the HO2S using the J 39194-B.
  12.  

To install:


NOTE
A special anti-seize compound is used on the HO2S threads. The compound consists of graphite suspended in fluid and glass beads. The graphite will burn away, but the glass beads will remain, making the sensor easier to remove. New or service sensors will already have the compound applied to the threads. If a sensor is removed from an engine and is to be reinstalled, the threads must have anti-seize compound applied before the reinstallation.

  1. Coat the threads of the HO2S with anti-seize compound.
  2.  
  3. Install and tighten the HO2S to 31 ft. lbs. (42 Nm).
  4.  
  5. Connect the engine wiring harness electrical connector to the HO2S electrical connector.
  6.  
  7. Install the CPA retainer.
  8.  
  9. Install the HO2S electrical connector rosebud clip to the ignition coil bracket.
  10.  
  11. Install the intake manifold cover.
  12.  

Bank 1 Sensor 2
  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Raise and support the vehicle.
  4.  
  5. Remove the Connector Position Assurance (CPA) retainer.
  6.  
  7. Disconnect the engine heated oxygen sensor (HO2S) electrical connector from the engine wiring harness electrical connector.
  8.  
  9. Remove the HO2S using the J 39194-B.
  10.  

To install:

  1. Coat the threads of the HO2S with anti-seize compound.
  2.  
  3. Install and tighten the HO2S to 31 ft. lbs. (42 Nm).
  4.  
  5. Connect the engine HO2S electrical connector to the engine wiring harness electrical connector.
  6.  
  7. Install the CPA retainer.
  8.  
  9. Lower the vehicle.
  10.  

Bank 2 Sensor 1
  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Remove the Connector Position Assurance (CPA) retainer.
  4.  
  5. Disconnect the engine wiring harness electrical connector from the heated oxygen sensor (HO2S) electrical connector.
  6.  
  7. Remove the HO2S rosebud clip from the oil level indicator tube tab.
    NOTE
    The oxygen sensor may be difficult to remove when the engine temperature is below 48°C (120°F). Excessive force may damage threads in the exhaust manifold or the exhaust pipe.

  8.  
  9. Remove the HO2S using the J 39194-B.
  10.  

To install:

  1. Coat the threads of the HO2S with anti-seize compound.
  2.  
  3. Install and tighten the HO2S to 31 ft. lbs. (42 Nm).
  4.  
  5. Connect the engine HO2S electrical connector to the engine wiring harness electrical connector.
  6.  
  7. Install the CPA retainer.
  8.  
  9. Lower the vehicle.
  10.  

Bank 2 Sensor 2
  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Raise and support the vehicle.
  4.  
  5. Remove the Connector Position Assurance (CPA) retainer.
  6.  
  7. Disconnect the engine heated oxygen sensor (HO2S) electrical connector from the engine wiring harness electrical connector.
  8.  
  9. Remove the HO2S using the J 39194-B.
  10.  

To install:

  1. Coat the threads of the HO2S with anti-seize compound.
  2.  
  3. Install and tighten the HO2S to 31 ft. lbs. (42 Nm).
  4.  
  5. Connect the engine HO2S electrical connector to the engine wiring harness electrical connector.
  6.  
  7. Install the CPA retainer.
  8.  
  9. Lower the vehicle.
  10.  

Testing



  1. Ignition OFF, disconnect the scan tool and wait 60 seconds to ensure all modules are powered down.
  2.  
  3. Ignition OFF, disconnect the harness connector at the appropriate HO2S.
  4.  
  5. Ignition OFF, measure for less than 5 ohms resistance between the appropriate HO2S low signal circuit terminal A and ground.
  6.  
  7. If more than the specified range, test the appropriate HO2S low signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  8.  
  9. Ignition ON, verify the appropriate scan tool HO2S parameter is approximately 450 mV.
  10.  
  11. If more than the specified value, test the appropriate HO2S high signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  12.  
  13. If less than the specified value, test the appropriate HO2S high signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
  14.  
  15. Ignition ON, install a 3A fused jumper wire at the HO2S high signal circuit terminal B. Toggle the jumper wire between the HO2S low signal circuit terminal A and battery voltage. Verify the appropriate scan tool HO2S parameter toggles between 0 mV and approximately 1,000 mV
  16.  
  17. If the appropriate scan tool HO2S parameter does not toggle correctly, test the HO2S high signal circuit for an open/high resistance. If the circuits test normal, replace the ECM.
  18.  
  19. If all circuits test normal, replace the appropriate HO2S.

    Click image to see an enlarged view

    Fig. 2.2L (L61) Front 1 Engine Heated Oxygen Sensor (HO2S)



    Click image to see an enlarged view

    Fig. 2.2L (L61) Rear 2 Engine Heated Oxygen Sensor (HO2S)



    Click image to see an enlarged view

    Fig. 3.5L (LZ9) & 3.9L (LZ9) Bank 1 Sensor 1 Engine Heated Oxygen Sensor (HO2S)



    Click image to see an enlarged view

    Fig. 3.5L (LZ9) & 3.9L (LZ9) Bank 2 Sensor 1 Engine Heated Oxygen Sensor (HO2S)



    Click image to see an enlarged view

    Fig. 3.5L (LZ9) & 3.9L (LZ9) Bank 1 Sensor 2 Engine Heated Oxygen Sensor (HO2S)



    Click image to see an enlarged view

    Fig. 3.5L (LZ9) & 3.9L (LZ9) Bank 2 Sensor 2 Engine Heated Oxygen Sensor (HO2S)

  20.  

 
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