Pacifica 2006-2008

Heated Oxygen Sensor

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Operation



The sensor senses the oxygen concentration in the exhaust gas then converts it into a voltage and sends it on to the PCM. The PCM controls fuel injection based on the signal so that the air fuel ratio is maintained at the theoretical ration.

Removal & Installation



3.5L Engine

CAUTION
When disconnecting the sensor electrical connector, do not pull directly on wire going into sensor.

  1. Before servicing the vehicle, refer to the Precautions section.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Disconnect the heated oxygen sensor electrical connector.
  6.  
  7. Use a socket such as a crowfoot wrench to remove oxygen sensor.
  8.  

To install:


NOTE
When replacing an HO2S Sensor, the PCM RAM memory must be cleared, either by disconnecting the PCM C-1 connector or momentarily disconnecting the battery negative terminal. The NGC learns the characteristics of each HO2S heater element and these old values should be cleared when installing a new HO2S sensor. The customer may experience driveability issues if this is not performed.

  1. After removing the sensor, the threads must be cleaned with an 18 mm X 1.5 + 6E tap. If reusing the original sensor, coat the sensor threads with an anti-seize compound such as Loctite 771-64 or equivalent. New sensors have compound on the threads and do not require an additional coating. Tighten the sensor to 28 Nm (20 ft. lbs.) torque.
  2.  
  3. Connect the heated oxygen sensor electrical connector.
  4.  
  5. Install the wiring clip to the heat shield.
  6.  
  7. Connect the negative battery cable.

    Click image to see an enlarged view

    Fig. HO2S sensor location-3.5L engine

  8.  

3.8L Engine
Downstream Sensor

CAUTION
When disconnecting the sensor electrical connector, do not pull directly on wire going into sensor.

  1. Before servicing the vehicle, refer to the Precautions section.
  2.  
  3. Disconnect negative battery cable.
  4.  
  5. Raise and support vehicle.
  6.  
  7. Disconnect the electrical connector.
  8.  
  9. Use a socket such as a crowfoot wrench to remove oxygen sensor.
  10.  

To install:


NOTE
When replacing an HO2S Sensor, the PCM RAM memory must be cleared, either by disconnecting the PCM C-1 connector or momentarily disconnecting the battery negative terminal. The NGC learns the characteristics of each HO2S heater element and these old values should be cleared when installing a new HO2S sensor. The customer may experience driveability issues if this is not performed.

  1. After removing the sensor, the threads must be cleaned with an 18 mm X 1.5 + 6E tap. If reusing the original sensor, coat the sensor threads with an anti-seize compound such as Loctite 771-64 or equivalent. New sensors have compound on the threads and do not require an additional coating. Tighten the sensor to 28 Nm (20 ft. lbs.) torque.
  2.  
  3. Connect the heated oxygen sensor electrical connector.
  4.  
  5. Connect the negative battery cable.

    Click image to see an enlarged view

    Fig. Downstream sensor location-3.8L engine

  6.  

Upstream Sensor

CAUTION
When disconnecting the sensor electrical connector, do not pull directly on wire going into sensor.

  1. Before servicing the vehicle, refer to the Precautions section.
  2.  
  3. Disconnect negative battery cable.
  4.  
  5. Disconnect the upper HO2S sensor connector.
  6.  
  7. Use a socket such as a crowfoot wrench to remove oxygen sensor.
  8.  

To install:


NOTE
When replacing an HO2S Sensor, the PCM RAM memory must be cleared, either by disconnecting the PCM C-1 connector or momentarily disconnecting the battery negative terminal. The NGC learns the characteristics of each HO2S heater element and these old values should be cleared when installing a new HO2S sensor. The customer may experience driveability issues if this is not performed.

  1. After removing the sensor, the threads must be cleaned with an 18 mm X 1.5 + 6E tap. If reusing the original sensor, coat the sensor threads with an anti-seize compound such as Loctite 771-64 or equivalent. New sensors have compound on the threads and do not require an additional coating. Tighten the sensor to 28 Nm (20 ft. lbs.) torque.
  2.  
  3. Connect the heated oxygen sensor electrical connector.
  4.  
  5. Connect the negative battery cable.

    Click image to see an enlarged view

    Fig. Upstream sensor location-3.8L engine

  6.  

4.0L Engine
  1. Before servicing the vehicle, refer to the Precautions section.
  2.  
  3. Disconnect negative battery cable.
  4.  
  5. Raise and support the vehicle safely.
  6.  
  7. Disconnect the wiring harness retaining clips, if equipped.
  8.  
  9. Disconnect the electrical connector from the sensor.
  10.  
  11. Remove the sensor from its mounting.
  12.  

To install:


NOTE
Threads on a new oxygen sensor are factory coated with anti-seize compound, to aid in removal. Do not add any additional anti-seize compounds to the threads of a new sensor.

  1. Installation is the reverse of the removal procedure.
  2.  
  3. Tighten the sensor to 30 ft. lbs.

    Click image to see an enlarged view

    Fig. HO2S sensor location (side one)-4.0L engine



    Click image to see an enlarged view

    Fig. HO2S sensor location (side two)-4.0L engine

  4.  

Testing




NOTE
Allow the HO2S Sensor to cool down before conducting the test. The HO2S Sensor voltage should stabilize at 5.0 volts. Raising the hood may help in reducing under hood temps quicker.

  1. Before servicing the vehicle, refer to the Precautions section.
  2.  
  3. Turn the ignition on, engine not running. With the scan tool, actuate the HO2S Heater Test.
  4.  
  5. With the scan tool, monitor HO2S Sensor voltage for at least 2 minutes. Does the HO2S Sensor voltage stay above 4.5 volts- If so, sensor is normal.
  6.  
  7. If voltage does not stay above 4.5v as indicated, check wiring and connectors. Check HO2S sensor for contamination.
  8.  
  9. If wiring from the HO2S sensor is damaged, DO NOT repair it; replace the HO2S sensor.
  10.  
  11. Turn the ignition off. Allow the HO2S sensor to cool down to room temperature.
  12.  
  13. Disconnect the HO2S Sensor harness connector.
  14.  
  15. Measure the resistance across the HO2S Sensor Heater element component side. Resistance for either HO2S Sensor should be 2.1-2.7 ohms.
  16.  
  17. If the HO2S Sensor is not within range, turn the ignition off.
  18.  
  19. Disconnect the HO2S Sensor harness connector. Turn the ignition to ON; engine not running.
  20.  
  21. With the proper scan tool, actuate the HO2S Heater Test.
  22.  
  23. Using a 12-volt test light connected to ground, probe the HO2S Heater Control circuit in the HO2S Sensor harness connector.
  24.  
  25. If the test light illuminates brightly and flashes on and off, replace the HO2S Sensor.
  26.  
  27. Confirm the repair with the appropriate Verification Test.
  28.  
  29. Turn the ignition off.
  30.  
  31. Disconnect the HO2S Sensor harness connector.
  32.  
  33. Disconnect the PCM harness connector.
  34.  
  35. Measure the resistance between ground and the HO2S Heater Control circuit in the HO2S Sensor harness connector.
  36.  
  37. Is the resistance below 5.0 ohms- If yes, repair the short to ground in the HO2S Sensor Heater Control circuit. If resistance is okay, go to step 20.
  38.  
  39. Confirm the repair.
  40.  
  41. If resistance was okay when measured in step 17, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.
  42.  
  43. If the resistance is still not within specified range, replace and program the Powertrain Control Module in accordance with the service information.
  44.  
  45. Confirm the repair.
  46.  

 
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