LaCrosse 2006-2007

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. A heating element inside the HO2S minimizes the time required for the sensor to reach operating temperature. Voltage is provided to the heater by the ignition 1 voltage circuit through a fuse. With the engine running, a ground is provided to the heater by the HO2S heater low control circuit through a low side driver within the Powertrain Control Module (PCM). The PCM commands the heater ON or OFF to maintain a specific HO2S operating temperature range. The PCM monitors the voltage on the HO2S heater low control circuit for heater fault diagnosis. If the PCM detects that the HO2S heater low control circuit voltage is not within a specified range, a DTC is set.

Removal & Installation



3.6L Engine
Heated Oxygen Sensor-1

WARNING
The Heated Oxygen Sensor (HO2S) uses a permanently attached pigtail and connector. Do not remove this pigtail from the HO2S. Damage or the removal of the pigtail or the connector could affect the proper operation of the sensor. Take care when handling the HO2S. Keep the in-line electrical connector, and the louvered end, free of grease, dirt, or other contaminants. Also avoid using cleaning solvents of any type. Do not drop the HO2S. Do not roughly handle the HO2S.

  1. Disconnect the HO2S electrical connector.
    WARNING
    The use of excessive force may damage the threads in the exhaust manifold/pipe.


    NOTE
    If the engine temperature is not above 120°F (48°C), the oxygen sensor may be difficult to remove.

  2.  
  3. Remove the HO2S.

    Click image to see an enlarged view

    Fig. Location of the heated oxygen sensor 1-3.6L engine

  4.  

To install:


NOTE
A special anti-seize compound is used on the oxygen sensor threads. New service sensors should already have the compound applied to the threads. Coat the threads of a reused sensor with anti-seize compound P/N 5613695 or equivalent.

  1. Install the HO2S. Tighten the HO2S 1 to 31 ft. lbs. (42 Nm).
  2.  
  3. Connect the HO2S electrical connector.
  4.  

Heated Oxygen Sensor-2

WARNING
The Heated Oxygen Sensor (HO2S) uses a permanently attached pigtail and connector. Do not remove this pigtail from the HO2S. Damage or the removal of the pigtail or the connector could affect the proper operation of the sensor. Take care when handling the HO2S. Keep the in-line electrical connector, and the louvered end, free of grease, dirt, or other contaminants. Also avoid using cleaning solvents of any type. Do not drop the HO2S. Do not roughly handle the HO2S.

  1. Raise and support the vehicle.
  2.  
  3. Disconnect the HO2S electrical connector.
    WARNING
    The use of excessive force may damage the threads in the exhaust manifold/pipe.


    NOTE
    If the engine temperature is not above 120°F (48°C), the oxygen sensor may be difficult to remove.

  4.  
  5. Remove the HO2S.

    Click image to see an enlarged view

    Fig. Location of the heated oxygen sensor 2-3.6L engine

  6.  

To install:


WARNING
Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.


NOTE
A special anti-seize compound is used on the oxygen sensor threads. New service sensors should already have the compound applied to the threads. Coat the threads of a reused sensor with anti-seize compound P/N 5613695 or equivalent.

  1. Install the HO2S. Tighten the HO2S 2 to 31 ft. lbs. (42 Nm).
  2.  
  3. Connect the HO2S electrical connector.
  4.  
  5. Lower the vehicle.
  6.  

3.8L Engine
Heated Oxygen Sensor-1

WARNING
The Heated Oxygen Sensor (HO2S) uses a permanently attached pigtail and connector. Do not remove this pigtail from the HO2S. Damage to the pigtail or the connector could affect the proper operation of the sensor. Take care when handling the HO2S. Keep the in-line electrical connector, and the louvered end, free of grease, dirt, or other contaminants. Also avoid using cleaning solvents of any type. Do not drop the HO2S. Do not roughly handle the HO2S.


NOTE
The oxygen sensor may be difficult to remove when the engine temperature is below 120°F (48°C). Excessive force may damage threads in the exhaust manifold or the exhaust pipe.

  1. Remove the fuel injector sight shield.
  2.  
  3. Remove the HO2S retaining clip.
  4.  
  5. Disconnect the HO2S electrical connector (1).
  6.  
  7. Remove the HO2S electrical connector (1) from the fuel injector sight shield bracket.
  8.  
  9. Use the oxygen sensor wrench, J 39194, to remove the HO2S (2) from the right exhaust manifold.

    Click image to see an enlarged view

    Fig. Location of the heated oxygen sensor 1-3.8L engine

  10.  

To install:


NOTE
A special anti-seize compound is used on the oxygen sensors threads. New service sensors should already have the compound applied to the threads. Coat the threads of a reused sensor with anti-seize compound GM P/N 12377953 or equivalent.

  1. Install the HO2S (2) to the right exhaust manifold. Use the oxygen sensor wrench, J 39194, to tighten the HO2S to 31 ft. lbs. (42 Nm).
  2.  
  3. Install the HO2S electrical connector (1) to the fuel injector sight shield bracket.
  4.  
  5. Connect the HO2S electrical connector (1).
  6.  
  7. Install the HO2S retaining clip.
  8.  
  9. Install the fuel injector sight shield.
  10.  

Heated Oxygen Sensor-2

WARNING
The Heated Oxygen Sensor (HO2S) uses a permanently attached pigtail and connector. Do not remove this pigtail from the HO2S. Damage to or the removal of the pigtail or the connector could affect the proper operation of the sensor. Take care when handling the HO2S. Keep the in-line electrical connector, and the louvered end, free of grease, dirt, or other contaminants. Also, avoid using cleaning solvents of any type. Do not drop the HO2S. Do not roughly handle the HO2S.


NOTE
The oxygen sensor may be difficult to remove when the engine temperature is below 120°F (48°C). Excessive force may damage threads in the exhaust manifold or the exhaust pipe.

  1. Raise and support the vehicle.
  2.  
  3. Remove the HO2S electrical connector retaining clip from the HO2S electrical harness connector.
  4.  
  5. Disconnect the HO2S electrical connector from the HO2S electrical harness connector.
  6.  
  7. Use the oxygen sensor wrench, J 39194, to remove the HO2S from the exhaust pipe.

    Click image to see an enlarged view

    Fig. Location of the heated oxygen sensor 2-3.8L engine

  8.  

To install:


NOTE
A special anti-seize compound is used on the HO2S threads. New service sensors should already have the compound applied to the threads. Coat the threads of a reused sensor with anti-seize compound GM P/N 12377953 or equivalent.

  1. Install the HO2S to the exhaust pipe. Use the oxygen sensor wrench, J 39194, to tighten the HO2S to 31 ft. lbs. (42 Nm).
  2.  
  3. Connect the HO2S electrical connector to the HO2S electrical harness connector.
  4.  
  5. Install the HO2S electrical connector retaining clip to the HO2S electrical harness connector.
  6.  
  7. Lower the vehicle.
  8.  

Testing





Click image to see an enlarged view

Fig. HO2S sensor 1 connector end view-3.6L engine



Click image to see an enlarged view

Fig. HO2S sensor 2 connector end view-3.6L engine



Click image to see an enlarged view

Fig. HO2S sensor 1 connector end view (NU6)-3.8L engine



Click image to see an enlarged view

Fig. HO2S sensor 1 connector end view (without NU6)-3.8L engine



Click image to see an enlarged view

Fig. HO2S sensor 2 connector end view-3.8L engine

  1. With an OBD2 scan tool connected to the datalink port:
    1. Start the engine and allow it to reach normal operating temperature.
    2.  
    3. If the engine is at operating temperature when started, wait 15 seconds to allow the heated oxygen sensor (HO2S) heater current to stabilize.
    4.  
    5. Observe the affected HO2S heater parameter with a scan tool.
    6.  
    7. The HO2S heater parameter should be within the specified range: 0.5-2.0 Amps.
    8.  

  2.  
  3. Replace the affected HO2S as necessary.
  4.  
  5. Probe for circuit voltage:
    1. Turn engine OFF.
    2.  
    3. Disconnect the affected HO2S.
    4.  
    5. Turn ON the ignition, with the engine OFF.
    6.  
    7. Probe the ignition 1 voltage circuit of the HO2S harness connector on the engine harness side with a test lamp that is connected to a good ground.
    8.  
    9. The test lamp should illuminate.
    10.  

  6.  
  7. Test the ground circuit:
    1. Turn OFF the ignition.
    2.  
    3. Probe the HO2S heater low control circuit of the HO2S harness connector on the engine harness side with a test lamp connected to battery voltage.
    4.  
    5. With the ignition still OFF, observe the test lamp.
    6.  
    7. The test lamp should illuminate.
    8.  

  8.  
  9. If the ECM and all circuits test normal, replace the appropriate HO2S.
  10.  

 
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