Pacifica, 2003-2005

Heated Oxygen Sensor

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Removal & Installation



3.5L

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

  1. Disconnect the negative battery cable.
  2.  
  3. Disconnect the heated oxygen sensor electrical connector.
  4.  
  5. Use a socket such as a crowfoot wrench to remove oxygen sensor.
  6.  

To Install:


NOTE
When replacing an O2 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 O2 heater element and these old values should be cleared when installing a new O2 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.

  8.  

3.8L Downstream Sensor

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

  1. Disconnect negative battery cable.
  2.  
  3. Raise and support vehicle.
  4.  
  5. Disconnect the electrical connector.
  6.  
  7. Use a socket such as a crowfoot wrench to remove oxygen sensor.
  8.  

3.8L Upstream & Downstream Sensors

NOTE
When replacing an O2 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 O2 heater element and these old values should be cleared when installing a new O2 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.
  6.  

3.8L Upstream Sensor

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

  1. Disconnect negative battery cable.
  2.  
  3. Disconnect the upper O2 sensor connector.
  4.  
  5. Use a socket such as a crowfoot wrench to remove oxygen sensor.

    Click image to see an enlarged view

    Fig.



    Click image to see an enlarged view

    Fig.

  6.  

To Install:

Testing




NOTE
Allow the O2 Sensor to cool down before conducting the test. The O2 Sensor voltage should stabilize at 5.0 volts. Raising the hood may help in reducing under hood temps quicker.

  1. Turn the ignition on, engine not running. With the scan tool, actuate the O2 Heater Test.
  2.  
  3. With the scan tool, monitor O2 Sensor voltage for at least 2 minutes. Does the O2 Sensor voltage stay above 4.5 volts- If so, sensor is normal.
  4.  
  5. If voltage does not stay above 4.5v as indicated, check wiring and connectors. Check O2 sensor for contamination.
  6.  
  7. If wiring from the O2 sensor is damaged, DO NOT repair it; replace the O2 sensor.
  8.  
  9. Turn the ignition off. Allow the O2 sensor to cool down to room temperature.
  10.  
  11. Disconnect the O2 Sensor harness connector.
  12.  
  13. Measure the resistance across the O2 Sensor Heater element component side. Resistance for either O2 Sensor should be 2.1-2.7 ohms.
  14.  
  15. If the O2 Sensor is not within range, turn the ignition off.
  16.  
  17. Disconnect the O2 Sensor harness connector. Turn the ignition to ON; engine not running.
  18.  
  19. With the proper scan tool, actuate the O2 Heater Test.
  20.  
  21. Using a 12-volt test light connected to ground, probe the O2 Heater Control circuit in the O2 Sensor harness connector.
  22.  
  23. If the test light illuminates brightly and flashes on and off, replace the O2 Sensor.
  24.  
  25. Confirm the repair with the appropriate Verification Test.
  26.  
  27. Turn the ignition off.
  28.  
  29. Disconnect the O2 Sensor harness connector.
  30.  
  31. Disconnect the PCM harness connector.
  32.  
  33. Measure the resistance between ground and the O2 Heater Control circuit in the O2 Sensor harness connector.
  34.  
  35. Is the resistance below 5.0 ohms- If yes, repair the short to ground in the O2 Sensor Heater Control circuit. If resistance is okay, go to step 20.
  36.  
  37. Confirm the repair.
  38.  
  39. 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.
  40.  
  41. If the resistance is still not within specified range, replace and program the Powertrain Control Module in accordance with the service information.
  42.  
  43. Confirm the repair.
  44.  

 
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