What is the purpose of an O2 sensor on a vehicles motor.?

Question

What is the purpose of an O2 sensor on a vehicles motor.?

Answer 1

simply put it is there to tell the cpu how efficient the engine is, so that thee cpu can adjust the injector pulse width accordingly.

Answer 2

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Answer 3

It sends a feedback signal based on the burnt exhaust gases back to the ECU which then adjusts the duty cycle of the injectors and maximises the fuel efficiency to a stoichometrically correct amount based on the fuel maps contained in the ECU.

Also known as a Lambda sensor, and thus 'closed loop lambda control'

Answer 4

For fuel to burn ideally there should be a ratio of 14.7:1 air to fuel. This is called the stochiometric ratio. At this ratio, all the fuel will be consumed with no air or unburned hydrocarbons remaining. Below stochiometric, there will be excessive hydrocarbons in the exhaust, above this ratio, there will be excessive air (which results in nitrogen oxides). So maintaining stochiometric ratio precisely is key to low emissions. The O2 sensor is usually located in the exhaust manifold or near the catalytic converter. It provides an electronic signal proportional to the fuel ratio. This is fed to the car's ECU, which is the computer which controls the fuel injection system. The ECU will then adjust the amount of fuel delivered to the injectors, maintaining the correct air/fuel ratio.

If your O2 sensor malfunctions, your engine would simply be a mess. Either it would run too rich, producing gobs of smoky pollutants and poor fuel economy, or it would run too lean, with poor power and high NOx emissions.  

Answer 5

It reads the oxygen output through the exhaust and with it gives a signal to the computer which determines to either rich or lean the mixture. Of course its also an emission control device but is well used nowadays to get what impressive power and fuel economy you get in modern engines.