Altima 2007-2009

Heated Oxygen Sensor

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Location



2.5L Engine

Specific to:

Nissan Altima 2007-2008

Refer to the accompanying illustration for sensor location.

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Fig. The primary oxygen sensor (air/fuel ratio sensor) is in the intake manifold below the heat shield-2.5L engine shown.

Specific to:

Nissan Altima 2009-2010



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Fig. Heated oxygen sensor 2 (11) showing the connector (12) and oil pan (13)-2.5L engine

3.5L Engine

Specific to:

Nissan Altima 2007-2008

Refer to the accompanying illustration for sensor location.

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Fig. The primary oxygen sensors (air/fuel ratio sensors) are in the exhaust manifolds (arrows indicate front of vehicle)-3.5L engine

Specific to:

Nissan Altima 2009-2010

Heated oxygen sensor 2 is located downstream of the three way catalyst (manifold).

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Fig. Heated oxygen sensor 2 locations-3.5L engine

Operation



Specific to:

Nissan Altima 2007-2008

Air fuel ratio (A/F) Sensor 1 is a planar one-cell current-limiting sensor. It is capable of precise measurement of lambda (-= 1), but it can also measure in the lean and rich ranges. The sensor element is composed of an electrode layer that carries voltage supplied by the ECM. A lean A/F ratio allows more oxygen to reach the sensor, which allows more current flow through the element, so more of the reference voltage is returned to the ECM. A rich A/F ratio inhibits current flow through the element, reducing sensor output voltage. A heater is integrated in the sensor element to ensure the required operating temperature of about 1,472°F (800°C).

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Fig. A/F sensor output voltage increases as oxygen increases

These sensors are also used to monitor catalyst efficiency and are called Sensor 2 (on California models, there may also a Sensor 3). They are mounted in the exhaust system downstream of the catalytic converter.

Component Description

Specific to:

Nissan Altima 2009-2010

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:

Nissan Altima 2009-2010

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:

Nissan Altima 2009-2010

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

Removal & Installation



Specific to:

Nissan Altima 2007-2008

  1. Make sure the exhaust manifold is cool.
  2.  
  3. Unplug the connector and remove the sensor with an oxygen sensor wrench or socket.

    Click image to see an enlarged view

    Fig. The primary oxygen sensor (air/fuel ratio sensor) is in the intake manifold below the heat shield-2.5L engine shown.



    Click image to see an enlarged view

    Fig. The primary oxygen sensors (air/fuel ratio sensors) are in the exhaust manifolds (arrows indicate front of vehicle)-3.5L engine

  4.  

To install:

  1. Installation is the reverse of the removal procedure.
  2.  
  3. When installing, lightly coat the threads with anti-seize and torque to 23 ft. lbs. (31 Nm). Do not over tighten or the Malfunction Indicator Light (MIL) may turn on.
  4.  

Specific to:

Nissan Altima 2009-2010


NOTE
The manufacturer does not provide a specific Removal and Installation procedure for this component. Refer to the graphic(s) when servicing this component.

Testing



Specific to:

Nissan Altima 2007-2008

  1. Turn ignition switch OFF and wait at least 10 seconds before going to the next step.
  2.  
  3. Confirm that battery voltage is more than 11V with the engine at idle.
  4.  
  5. Start engine and warm it up to normal operating temperature.
  6.  
  7. Let it idle for 2 minutes and check for 1st trip DTC.
  8.  
  9. If the fault codes indicate oxygen sensor heater malfunction:
    WARNING
    Connect the voltmeter ground probe to engine or chassis ground. Do not test circuits with the meter connected to the battery or the ECM may be damaged.



    Turn the ignition switch OFF and unplug the sensor connector.
     
    With the ignition switch ON , check for battery voltage at terminal 3 on the wiring harness connector. This power comes through a fuse on the main fuse panel.
     



    With the ignition switch OFF , check continuity of the wiring harness between sensor terminal 4 and the ECM. Look for open circuits or short circuits to power. This is the sensor heater ground circuit.
     
    On the sensor itself, check resistance across terminals 3 and 4. On Sensor 1, heater resistance should be about 2 ohms at room temperature. On Sensor 2, heater resistance should be 3.3 to 4.4 ohms.
     

  10.  
  11. If the fault codes indicate sensor malfunction, connect a scan tool or oscilloscope and monitor oxygen sensor operation. Sensor 1 should output approximately 2.2 volts at steady no-load idle.
  12.  
  13. If the sensor does not perform correctly at idle or while driving, make sure the fuel injection and ignition systems are functioning properly and that the engine is mechanically sound.
  14.  
  15. If no other cause can be found for rich or lean operation, replace the sensor.
  16.  

Specific to:

Nissan Altima 2009-2010


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

Connection & Wiring Diagnosis

Specific to:

Nissan Altima 2009-2010

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:

Nissan Altima 2009-2010

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:

Nissan Altima 2009-2010

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. Normal pre-catalyst HO2S reading



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Fig. Normal post-catalyst HO2S reading

Post-Catalyst Sensor 2

Specific to:

Nissan Altima 2009-2010

A properly operating #2, or rear heated oxygen sensor (HO2S) should display flat feedback voltage of less than 0.2 volts DC . 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

Specific to:

Nissan Altima 2009-2010

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 Cause 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

Specific to:

Nissan Altima 2009-2010



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Fig. Related Diagnostic Trouble Codes

 
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