Oxygen Sensors

The oxygen sensor, located in the exhaust manifold, senses whether the air-fuel ratio is rich or lean, and sends signals to the ECU which in turn makes minor corrections to the amount of fuel being metered. This is necessary for the three-way catalytic converter to function properly.

There are two kinds of oxygen sensors: zirconia and titania. The zirconia oxygen sensor is constructed in a bulb configuration from zirconia dioxide. A thin platinum plate is attached to both the inside and outside of the bulb. The inner area is exposed to the atmosphere and the outside is exposed to the exhaust. When the sensor is heated to approximately 600°F, electrically

ZIRCONIA OXYGEN SENSOR

ZIRCONIA OXYGEN SENSOR

■ > Exhaust gas

charged oxygen ions form on the platinum plates. The amount of oxygen to which each plate is exposed determines how many ions form on the plates. When there is a difference in the number of ions on the plates, a difference in potential or voltage occurs between the two plates. The less oxygen there is in the exhaust, the greater the voltage produced. When the air-fuel mixture is lean, the voltage created is low. Conversely, when the mixture is rich, the voltage is high.

The titania oxygen sensor does not produce a voltage. Instead, it undergoes a change in resistance in relation to the oxygen content in the exhaust. This type of oxygen sensor is referred to as a thick film sensor. It consists of a piece of titania with two wires connected to it located at the end of an insulator. The sensor is not exposed to the atmosphere only to the exhaust. Because the operating temperature must remain constant, the sensor has an electric heater. After the

TITANIA OXYGEN SENSOR (Heating Element Not Shown)

TITANIA OXYGEN SENSOR (Heating Element Not Shown)

sensor is at operating temperature, the amount of oxygen to which the titania is exposed. will change the physical resistance of the sensor. The ECU supplies a reference voltage to the sensor and monitors the voltage at the signal wire, similar to a thermistor.

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Responses

  • Aziza
    How many oxygen sensors on a 2007 prius?
    3 years ago
  • hanna
    Is an ntk24642 oxygen sensor a Zirconia or titania?
    1 month ago
  • frediana giordano
    How many oxygen sensors does a 2010 totyota rav4 have?
    13 days ago

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