Catalyst System: Notes

The catalytic converter and exhaust systems work together to control the release of harmful engine exhaust emissions into the atmosphere. Engine exhaust gas consists mainly of Nitrogen (N), Carbon Dioxide (CO₂ ) and water vapor (H₂ O). However, it also contains Carbon Monoxide (CO), Oxides of Nitrogen (NO_x ), Hydrogen (H), and various unburned Hydrocarbons (HCs). CO, NO_x , and HCs are major air pollutants, and their emission into the atmosphere must be controlled. The exhaust system generally consists of an exhaust manifold, front exhaust pipe, upstream Heated Oxygen Sensor (HO2S), rear exhaust pipe, downstream HO2S, a muffler and an exhaust tailpipe. The catalytic converter is installed between front and rear exhaust pipes. Catalytic converter efficiency is monitored by the OBD-II system. For additional OBD-II Monitor information, see DIAGNOSTIC MONITORS  under COMPUTERIZED ENGINE CONTROLS.