The role of the sensor is to determine information on whether there is excess oxygen in the exhaust after engine combustion, i.e. oxygen content, and convert the oxygen content into a voltage signal to the engine computer, enabling the engine to achieve closed-loop control with excess air factor as the target; ensuring that the three-way catalytic converter has maximum conversion efficiency for all three pollutants in the exhaust, namely hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOX), for maximum conversion and purification of emission pollutants.