Catalytic Converter: Description and Operation

The three-way catalytic converter, together with the closed loop air/fuel ratio control (based on the oxygen sensor signal) oxidizes carbon monoxides (CO) and hydrocarbons (HC), and reduces nitrogen oxides (NOx).
When the mixture is controlled at stoichiometric air4uel ratio, the three-way catalytic converter provides the highest purification against CO, HO, and NOx.