(O2) Oxygen Sensor

Discussion in 'Parts Information' started by Codename.47, Jun 7, 2012.

  1. Codename.47

    Codename.47 Guest


    Zirconia Sensors: An important property of the Zirconia element is that it can conduct oxygen ions above a temperature of about 350°C. When the sensor is fitted, the outside of the Zirconia element is exposed to the exhaust gas and the inside is in contact with reference air.

    Both sides of the element are coated with a thin layer of platinum that act as electrodes and carry the sensors voltage signal from the Zirconia element to the lead wire. At operating temperature, oxygen ions are able to pass through the element and deposit a charge on the platinum electrode thus generating a voltage signal.

    If the AFR is rich, a high signal voltage is generated across the electrodes due to the difference in oxygen concentration present across the two sides of the element. Conversely, if the AFR is lean, a low voltage is generated across the electrodes due to the small difference in oxygen content between exhaust gases and the reference air inside the sensor.

    Zirconia Sensor Voltage vs. AFR GraphTitania Sensors: The Titania element in these sensors does not produce a voltage like the Zirconia element. The property of the Titania element which allows for the detection of oxygen in the exhaust gas is its electrical resistance. The electrical resistance of the Titania element changes according to the concentration of oxygen in the exhaust gas.

    The ECU supplies a voltage to the Titania sensor which depending on the presence, or lack of oxygen in the exhaust gas, will vary its resistance consequently changing the voltage signal returned back to the ECU relating to a lean or rich AFR.

    Due to their different properties Titania and Zirconia sensors should not be interchanged under any circumstance.

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  2. Codename.47

    Codename.47 Guest


    Visual inspection alone is not usually sufficient to determine if an oxygen sensor is functioning correctly. However, the following are considered mandatory basic checks:

    * The lead wire and connector should be checked for damage. Any damage will interfere with the sensor signal. Due to the fragile nature of the element it is possible for the sensor element to be critically damaged internally, despite the lack of physical external damage.
    * The sensor body should be checked for dents, which are a sign of mechanical shock that can crack the sensor element.
    * The appearance of the sensor's protector tube can give an indication of possible problems.
  3. Codename.47

    Codename.47 Guest

    Excessive White or Grey Deposits
    Excessive deposits such as these indicates that fuel additives are being used or the engine is burning oil. Certain components in the fuel additives and oil can contaminate the sensor element.

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  4. Codename.47

    Codename.47 Guest

    Excessive Carbon or Oil Deposits
    Excessive carbon and oil deposits can damage the sensor. Carbon deposits can clog the sensor and effect its response time. The cause can be a rich mixture, exhaust air leaks or high oil consumption due to worn piston rings or valve seals.

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  5. Codename.47

    Codename.47 Guest

    Shiny Deposits
    Shiny Deposits indicate the presents of lead. Lead attacks the platinum on the sensor and in the catalyst. The sensor should be changed and only unleaded fuel used.

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