The oxygen sensor is used to determine the engine exhaust oxygen if excess ,namely the content of oxygen,and the oxygen content is converted to a voltage signal then delivered to the engine computer,so that the engine can realize to excess air factor as the goal of the closed loop control.To ensure that three way catalytic converter on the exhaust of hydrocarbons(HC),carbon monoxide(CO)and nitrogen oxides(NOX)three kinds of hydrocarbons（HC） http://www.hongsean.com/