2007 Jeep Compass

Heated Oxygen Sensor

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Operation



Component Description

Specific to:

Jeep Compass 2007-2009

Jeep Patriot 2007-2009

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.

Fuel Trim

Specific to:

Jeep Compass 2007-2009

Jeep Patriot 2007-2009

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.

Oxygen Sensor Heater

Specific to:

Jeep Compass 2007-2009

Jeep Patriot 2007-2009

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

Removal & Installation



AWD Models
Downstream Sensor

Specific to:

Jeep Compass 2007-2009

Jeep Patriot 2007-2009


CAUTION
The exhaust manifold, exhaust pipes, and catalytic converter(s) become very hot during engine operation. Allow the engine to cool before removing the oxygen sensor. Failure to allow the engine to cool before removal may result in personal injury caused by burns.


WARNING
When disconnecting the sensor electrical connector, do not pull directly on the wires going into the oxygen sensor as damage to the oxygen sensor may occur.


NOTE
Use an Oxygen Sensor (O2S) removal tool for this procedure.

  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Raise and safely support the vehicle.
  4.  
  5. Disconnect the O2S wire harness mounting clips from the engine or body, if equipped.
  6.  
  7. Disconnect the O2S pigtail harness connector (1) from the engine wiring harness.
  8.  
  9. Remove the O2S (3) from the exhaust pipe (2).

    Click image to see an enlarged view

    Fig. Heated Oxygen Sensor (HO2S) (downstream 1/2)-AWD models

  10.  

To install:


NOTE
The threads of new oxygen sensors are factory coated with anti-seize compound to aid in removal. DO NOT add any additional anti-seize compound to the threads of a new O2S.


WARNING
When Equipped: The O2S pigtail harness must be clipped and/or bolted back to original positions on the engine or body to prevent mechanical damage to the wiring.

  1. Install the O2S (3) to the exhaust pipe (2). Tighten to 30 ft. lbs. (41 Nm).
  2.  
  3. Connect the O2S pigtail harness connector (1) to the engine wiring harness.
  4.  
  5. Connect the O2S wire harness mounting clips to the engine or body, if equipped.
  6.  

Upstream Sensor

Specific to:

Jeep Compass 2007-2009

Jeep Patriot 2007-2009


CAUTION
The exhaust manifold, exhaust pipes, and catalytic converter(s) become very hot during engine operation. Allow the engine to cool before removing the oxygen sensor. Failure to allow the engine to cool before removal may result in personal injury caused by burns.


WARNING
When disconnecting the sensor electrical connector, do not pull directly on the wires going into the oxygen sensor as damage to the oxygen sensor may occur.


NOTE
Use an Oxygen Sensor (O2S) removal tool for this procedure.

  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Raise and safely support the vehicle.
  4.  
  5. Disconnect the O2S wire harness mounting clips from the engine or body, if equipped.
  6.  
  7. Disconnect the O2S pigtail harness connector (1) from the engine wiring harness.
  8.  
  9. Remove the O2S (3) from the maniverter (2).

    Click image to see an enlarged view

    Fig. Heated Oxygen Sensor (HO2S) (upstream 1/1)-AWD models

  10.  

To install:


NOTE
The threads of new oxygen sensors are factory coated with anti-seize compound to aid in removal. DO NOT add any additional anti-seize compound to the threads of a new O2S.


WARNING
When Equipped: The O2S pigtail harness must be clipped and/or bolted back to original positions on the engine or body to prevent mechanical damage to the wiring.

  1. Install the O2S (3) to the maniverter (2). Tighten to 30 ft. lbs. (41 Nm).
  2.  
  3. Connect the O2S pigtail harness connector (1) to the engine wiring harness.
  4.  
  5. Connect the O2S wire harness mounting clips to the engine or body, if equipped.
  6.  

FWD Models
Downstream Sensor

Specific to:

Jeep Compass 2007-2009

Jeep Patriot 2007-2009


CAUTION
The exhaust manifold, exhaust pipes, and catalytic converter(s) become very hot during engine operation. Allow the engine to cool before removing the oxygen sensor. Failure to allow the engine to cool before removal may result in personal injury caused by burns.


WARNING
When disconnecting the sensor electrical connector, do not pull directly on the wires going into the oxygen sensor as damage to the oxygen sensor may occur.


NOTE
Use an Oxygen Sensor (O2S) removal tool for this procedure.

  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Raise and safely support the vehicle.
  4.  
  5. Disconnect the O2S wire harness mounting clips from the engine or body, if equipped.
  6.  
  7. Disconnect the O2S pigtail harness connector (1) from the engine wiring harness.
  8.  
  9. Remove the O2S (3) from the catalytic converter (2).

    Click image to see an enlarged view

    Fig. Heated Oxygen Sensor (HO2S) (downstream 1/2)-FWD models

  10.  

To install:


NOTE
The threads of new oxygen sensors are factory coated with anti-seize compound to aid in removal. DO NOT add any additional anti-seize compound to the threads of a new O2S.


WARNING
When Equipped: The O2S pigtail harness must be clipped and/or bolted back to original positions on the engine or body to prevent mechanical damage to the wiring.

  1. Install the O2S (3) to the catalytic converter (2). Tighten to 30 ft. lbs. (41 Nm).
  2.  
  3. Connect the O2S pigtail harness connector (1) to the engine wiring harness.
  4.  
  5. Connect the O2S wire harness mounting clips to the engine or body, if equipped.
  6.  

Upstream Sensor

Specific to:

Jeep Compass 2007-2009

Jeep Patriot 2007-2009


CAUTION
The exhaust manifold, exhaust pipes, and catalytic converter(s) become very hot during engine operation. Allow the engine to cool before removing the oxygen sensor. Failure to allow the engine to cool before removal may result in personal injury caused by burns.


WARNING
When disconnecting the sensor electrical connector, do not pull directly on the wires going into the oxygen sensor as damage to the oxygen sensor may occur.


NOTE
Use an Oxygen Sensor (O2S) removal tool for this procedure.

  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Raise and safely support the vehicle.
  4.  
  5. Disconnect the O2S wire harness mounting clips from the engine or body, if equipped.
  6.  
  7. Disconnect the O2S pigtail harness connector (1) from the engine wiring harness.
  8.  
  9. Remove the O2S (3) from the exhaust pipe (2).

    Click image to see an enlarged view

    Fig. Heated Oxygen Sensor (HO2S) (upstream 1/1)-FWD models

  10.  

To install:


NOTE
The threads of new oxygen sensors are factory coated with anti-seize compound to aid in removal. DO NOT add any additional anti-seize compound to the threads of a new O2S.


WARNING
When Equipped: The O2S pigtail harness must be clipped and/or bolted back to original positions on the engine or body to prevent mechanical damage to the wiring.

  1. Install the O2S (3) to the exhaust pipe (2). Tighten to 30 ft. lbs. (41 Nm).
  2.  
  3. Connect the O2S pigtail harness connector (1) to the engine wiring harness.
  4.  
  5. Connect the O2S wire harness mounting clips to the engine or body, if equipped.
  6.  

Testing




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

Connection And Wiring Diagnosis

Specific to:

Jeep Compass 2007-2009

Jeep Patriot 2007-2009

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

Specific to:

Jeep Compass 2007-2009

Jeep Patriot 2007-2009

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

Specific to:

Jeep Compass 2007-2009

Jeep Patriot 2007-2009

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.

Click image to see an enlarged view

Fig. Normal pre-catalyst HO2S reading.



Click image to see an enlarged view

Fig. Normal post-catalyst HO2S reading.

Post-Catalyst HO2S (Sensor 2)

Specific to:

Jeep Compass 2007-2009

Jeep Patriot 2007-2009

A properly operating No. 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 HO2S (Sensor 1)

Specific to:

Jeep Compass 2007-2009

Jeep Patriot 2007-2009

A properly operating No. 1, or front Heated Oxygen Sensor (HO2S) should display a cross count of 8 oscillations or more within 10 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 (DTC)

Specific to:

Jeep Compass 2007-2009

Jeep Patriot 2007-2009



Click image to see an enlarged view

Fig. Related Diagnostic Trouble Codes

 
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