All About O2 sensor.

11- 05- 2022
By PanPeter

 What is Oxygen Sensor Air/Fuel Sensor:
    A critical component of today’s modern vehicle is the sensor measuring the exhaust gases. This sensor works with the vehicle Electronic Control Unit (ECU) to constantly maintain the operational efficiency of the engine. If the oxygen content in the exhaust gas is too high (a lean mixture) or too low (a rich mixture), the sensor is able to transmit this information back to the ECU, which then adjusts the air to fuel ratio.
   Not all vehicles have sensors with the same output characteristics and these sensors are not interchangeable. It is important to confirm sensor type before making the repair.
    In vehicles equipped with a heated oxygen sensor, the output voltage changes in accordance with the oxygen concentration in the exhaust gas. The ECU uses this output voltage to determine whether the present air/fuel ratio is richer or leaner than the stoichiometric air/fuel ratio (14.7:1).
    Vehicles equipped with an air/fuel ratio sensor have approximately 0.4 V constantly applied to the sensor, which outputs a current that varies in accordance with the oxygen concentration in the exhaust gas. The ECU converts the changes in the output current into voltage allowing a response that is directly proportional to the input of the present air/fuel ratio in the exhaust system.

How Many O2 Sensors Are There and Where Are They Located?

   Since 1981, most vehicles have been manufactured with one oxygen sensor per bank of cylinders. That's one on an inline engine and two on a V-shaped engine. The banks may be named as "left" and "right" or "front" and "rear" depending on how the engine is mounted in the engine bay.  These are located in the exhaust manifold or the exhaust pipe and are now known as "upstream" or "pre-cat" sensors, since they are located before the catalytic converter.    With new emission standards, vehicles from about 1996 forward also generally have sensors after the catalytic converter now known as "downstream" or "post-cat" sensors. Some cars with single bank engines may have two sensors in each position.    In general, recent car and truck models will have one upstream and one downstream sensor per bank, totaling either two or four O2 sensors.

How Do Oxygen Sensors Fail?

   Oxygen sensors have to exist in a pretty rough environment. The sensor itself is partly inside the very hot exhaust stream and is exposed to any number of different combustion byproducts. The rest of the sensor hangs out below the vehicle where it is exposed to all kinds of dirt and debris. It's no wonder that things occasionally go wrong. The sensor itself can become clogged with particulate matter or corroded by the various chemicals it encounters. The outside parts can be damaged by abrasive dirt and rocks. There is one rather obvious sign of a faulty oxygen sensor: the check engine light. Your oxygen sensor is the most likely culprit when the check engine light comes on.

O2 Sensors

 

 

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