Yaris 2007

Heated Oxygen Sensor

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Component Description



Specific to:

Toyota Yaris 2007-2010

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.

Location



Specific to:

Toyota Yaris 2007-2010

Refer to the accompanying illustration.

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Fig. Locating the HO2S sensor

Operation



Fuel Trim

Specific to:

Toyota Yaris 2007-2010

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:

Toyota Yaris 2007-2010

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

Removal & Installation



Specific to:

Toyota Yaris 2007-2010

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the center console. Refer to Curtain Airbag in the SRS section.
  4.  
  5. Disconnect the sensor connector.
  6.  
  7. Remove the grommet and pass the sensor connector out of the cabin through the floor panel.
  8.  
  9. Using SST 09224-00010, remove heated oxygen sensor No. 2.

    Click image to see an enlarged view

    Fig. Using SST 09224-00010, remove heated oxygen sensor No. 2

  10.  

Testing



Specific to:

Toyota Yaris 2007-2010


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

Connection & Wiring Diagnosis

Specific to:

Toyota Yaris 2007-2010

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:

Toyota Yaris 2007-2010

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:

Toyota Yaris 2007-2010

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:

Toyota Yaris 2007-2010

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:

Toyota Yaris 2007-2010

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:

Toyota Yaris 2007-2010



Click image to see an enlarged view

Fig. Related Diagnostic Trouble Codes

 
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