The working principle of zirconia oxygen sensor is as follows: the ceramic body of the zirconium tube is porous, and oxygen can penetrate into the porous body solid electrolyte. At higher temperatures, oxygen ionizes. As long as the oxygen content outside the zirconium tube (atmosphere) (exhaust gas) side is not the same, there is a difference in oxygen concentration, then in the solid electrolyte inside the oxygen ion diffusion from one side of the atmosphere to the exhaust side, so that the zirconium tube to form a microbattery, in the zirconium tube platinum electrode voltage. When the mixture is thin, the oxygen content in the exhaust is much, the difference of oxygen concentration on both sides is small, and the voltage generated is small; When the mixture concentration, oxygen content in exhaust is little, the content of CO, hc, NOx is more, these elements under the catalysis of zirconium tube outer surface platinum, react with oxygen, for the consumption of exhaust gas residual oxygen, make the zirconium tube outer surface oxygen concentration becomes zero, which makes the zirconium tube, oxygen concentration difference on either side of the outside suddenly increases, the voltage between the poles is also increased.

Therefore, the voltage generated by the oxygen sensor has a mutation around the excess air coefficient λ=1. When λ>1, the output voltage of the oxygen sensor is almost zero, and when λ<1, the output voltage of the oxygen sensor is close to 1V. In the engine mixture closed-loop control process, the oxygen sensor is equivalent to a concentration switch, according to the change of air fuel ratio of the mixture to the ECU input width change of the electrical pulse signal, ECU according to the oxygen sensor feedback signal, control the amount of fuel injection, so that the composition of harmful gases in the exhaust is reduced to the minimum.