9-3 1999

Heated Oxygen Sensor

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Location





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Fig. Front oxygen sensor-1998-2002 2.0L Engine



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Fig. Rear oxygen sensor-1998-2002 2.0L Engine



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Fig. Upper oxygen sensor-2003-2005 2.0L engine



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Fig. Lower oxygen sensor-2003-2005 2.0L engine



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Fig. Front oxygen sensor-2.3L engine



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Fig. Rear oxygen sensor-2.3L engine



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Fig. Front oxygen sensor (3)-3.0L engine



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Fig. Rear oxygen sensor (7) and cable retainers (6)-3.0L engine

Operation



The Oxygen Sensor is a zirconium dioxide electronic device that measures the proportion of oxygen (O2) content in the exhaust gas. The sensor operates by measuring the difference between the oxygen content in the exhaust gas and the external air, and generates a variable voltage signal as the ratio between the two changes. The function of the oxygen sensor is to monitor the air-fuel ratio of the engine, determine if the mixture is rich or lean, and provide feedback (real-time information) to the Powertrain Control Module (PCM) so that the air-fuel ratio may be automatically adjusted.

In order to achieve operating temperature and enter closed loop more quickly, modern oxygen sensors have built-in heating elements.

Fuel trim is the PCM parameter that is used to adjust the air-fuel mixture. The ideal HO2S feedback value is 0.45 volts DC, which is indicated when air and fuel are at the stoichiometric ratio of 14.7:1. This value is determined by oxygen sensor feedback, and provides the final data for the PCM in determining the correct air-fuel mixture.

Removal & Installation



2.0L Engine
Front
  1. Before servicing the vehicle, refer to the precautions.
    WARNING
    The cables must not be twisted. Twisted cables exposed to vibration can break. The oxygen sensor is sensitive to impacts and jolting and must be handled with care.

  2.  
  3. Remove the engine cover.
  4.  
  5. Remove the oxygen sensor connector from the holder by pressing the lugs together.
  6.  
  7. Remove the bypass pipe and heat shield.
  8.  
  9. Uncut the cable tie to the oxygen sensor and draw out the cables.
  10.  
  11. Remove the oxygen sensor from the turbo outlet pipe.

    Click image to see an enlarged view

    Fig. Front oxygen sensor

  12.  

To install:

  1. Coat the oxygen sensor threads with Molykote 1000 (30 20 971) to prevent binding.
  2.  
  3. Install the oxygen sensor. Tighten to 41 ft. lbs. (55 Nm).
    WARNING
    Chemicals such as contact spray and grease must not come into contact with the oxygen sensor connectors.

  4.  
  5. Draw out the cable and plug in the connector.
  6.  
  7. Fasten the cable to the water pipe with a cable tie.
  8.  
  9. Install the heat shield and bypass pipe. Tighten to 15 ft. lbs. (20 Nm).
  10.  
  11. Install the upper engine cover.
  12.  

Rear
  1. Before servicing the vehicle, refer to the precautions.
    WARNING
    The cables must not be twisted. Twisted cables exposed to vibration can break. The oxygen sensor is sensitive to impacts and jolting and must be handled with care.

  2.  
  3. Remove the engine cover.
  4.  
  5. Remove the oxygen sensor connector from the holder by pressing the lugs together.
  6.  
  7. Cut the cable tie to the oxygen sensor and draw out the cables.
  8.  
  9. Raise and safely support the vehicle securely on jackstands.
  10.  
  11. Pull down the cable and remove the oxygen sensor.
  12.  
  13. Coat the oxygen sensor threads with Molykote 1000 (30 20 971) to prevent binding.
  14.  

To install:

Click image to see an enlarged view

Fig. Rear oxygen sensor

  1. Install the oxygen sensor. Tighten to 41 ft. lbs. (55 Nm).
  2.  
  3. Lead the cable as far up as it will go.
  4.  
  5. Lower the vehicle.
  6.  
  7. Draw out the cable and plug in the connector.
  8.  
  9. Fasten the cable to the water pipe with a cable tie.
  10.  
  11. Install the upper engine cover.
  12.  

2.3L Engine
Front
  1. Before servicing the vehicle, refer to the precautions.
    WARNING
    The cables must not be twisted. Twisted cables exposed to vibration can break. The oxygen sensor is sensitive to impacts and jolting and must be handled with care.

  2.  
  3. Remove the engine cover.
  4.  
  5. Remove the oxygen sensor connector from the holder by pressing the lugs together.
  6.  
  7. Remove the bypass pipe and heat shield.
  8.  
  9. Uncut the cable tie to the oxygen sensor and draw out the cables.
  10.  
  11. Remove the oxygen sensor from the turbo outlet pipe.

    Click image to see an enlarged view

    Fig. Front oxygen sensor-2.3L engine

  12.  

To install:

  1. Coat the oxygen sensor threads with Molykote 1000 (30 20 971) to prevent binding.
  2.  
  3. Install the oxygen sensor. Tighten to 41 ft. lbs. (55 Nm).
    WARNING
    Chemicals such as contact spray and grease must not come into contact with the oxygen sensor connectors.

  4.  
  5. Draw out the cable and plug in the connector.
  6.  
  7. Fasten the cable to the water pipe with a cable tie.
  8.  
  9. Install the heat shield and bypass pipe. Tighten to 15 ft. lbs. (20 Nm).
  10.  
  11. Install the upper engine cover.
  12.  

Rear
  1. Before servicing the vehicle, refer to the precautions.
    WARNING
    The cables must not be twisted. Twisted cables exposed to vibration can break. The oxygen sensor is sensitive to impacts and jolting and must be handled with care.

  2.  
  3. Remove the engine cover.
  4.  
  5. Remove the oxygen sensor connector from the holder by pressing the lugs together.
  6.  
  7. Cut the cable tie to the oxygen sensor and draw out the cables.
  8.  
  9. Raise and safely support the vehicle securely on jackstands.
  10.  
  11. Pull down the cable and remove the oxygen sensor.
  12.  
  13. Coat the oxygen sensor threads with Molykote 1000 (30 20 971) to prevent binding.
  14.  

To install:

Click image to see an enlarged view

Fig. Rear oxygen sensor-2.3L engine

  1. Install the oxygen sensor. Tighten to 41 ft. lbs. (55 Nm).
  2.  
  3. Lead the cable as far up as it will go.
  4.  
  5. Lower the vehicle.
  6.  
  7. Draw out the cable and plug in the connector.
  8.  
  9. Fasten the cable to the water pipe with a cable tie.
  10.  
  11. Install the upper engine cover.
  12.  

Testing



Connection & Wiring Diagnosis

Refer to the Electrical Wiring Diagram for component and connector locations, connector views, and circuit-specific information.

Many intermittent open or short circuits may be caused by wiring harness and connector movement due to vibration, engine torque, bumps and rough pavement, etc.

  1. Test the wiring harness and connectors by performing the following tests:

    Move the related connectors and wiring while monitoring the appropriate scan tool data.
     
    Move the related connectors and wiring with the component commanded ON and OFF. Using a suitable the scan tool, observe the component operation.
     
    With the engine running, move the related connectors and wiring while monitoring component operation.
     
    If harness or connector movement affects the data displayed, the component and system operation, or the engine operation, inspect and repair the harness or connections as necessary.
     

  2.  
  3. Test the connector terminal pins and/or wiring by performing the following tests:

    Inspect for incorrect mating of the connector halves, or terminals not fully seated in the connector body.
     
    Inspect for improperly formed or damaged terminals and test for incorrect terminal tension.
     
    Inspect for poor terminal to wire connections including terminals crimped over insulation. This requires removing the terminal from the connector body.
     
    Inspect for corrosion or water intrusion. Pierced or damaged insulation can allow moisture to enter the wiring. The conductor can corrode inside the insulation with little visible evidence. Look for swollen and/or brittle sections of wire in the suspect circuits.
     
    Inspect for wires that are broken inside the insulation by gently pulling on suspect sections of wiring.
     

  4.  

Heated Oxygen Sensor Strategy

The oxygen sensor operates most effectively when an operating temperature of 1,472° F (800° C) or higher is reached and maintained. When the oxygen sensor reaches the specified temperature and begins sending the feedback signal, the PCM uses the information to enter closed loop mode, which is defined as the PCM having full control of the air-fuel ratio. In order to achieve operating temperature and enter closed loop more quickly, modern oxygen sensors have built-in heating elements.

Oxygen Sensor Heater

The oxygen sensor heater may be tested by performing a resistance test; the sensor must be disconnected from the main engine wiring harness. If the circuit resistance is greater than 5.0 ohms, replace the HO2S. Refer to the Electrical Wiring Diagram for specific circuit information and connector views.

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Fig. Figure 1: Normal pre-catalyst HO2S reading.



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Fig. Figure 2: Normal post-catalyst HO2S reading.

Post-Catalyst Sensor 2

A properly operating #2, or rear heated oxygen sensor (HO2S) should display flat feedback voltage of less than 0.2 volts DC (See Figure 2). Use a suitable scan tool or a Graphing Multi-Meter (GMM) in order to view HO2S data.

If the feedback signal displays a cross-count, this is usually an indication of a faulty catalytic converter. If the feedback signal is flat, but is greater than 0.5 volts DC, additional diagnosis is required in order to determine the proper function of the HO2S, or if a fault exists in any related sub-systems.

Pre-Catalyst Sensor 1

A properly operating #1, or front heated oxygen sensor (HO2S) should display a cross count of eight oscillations or more within ten seconds, within a voltage range of 0.2 - 0.8 volts DC (See Figure 1). Use a suitable scan tool or a Graphing Multi-Meter (GMM) in order to view HO2S data.

If the feedback signal is not within the specified range, additional diagnosis is required in order to determine the proper function of the HO2S, or if a fault exists in any related sub-systems.

Related Diagnostic Trouble Codes


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Fig. Related Diagnostic Trouble Codes

 
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