The catalytic converter has been on US built cars and light trucks since the mid 1970's.   The purpose of the catalytic converter is to reduce the exhaust emissions of the internal combustion engine. The internal construction of the converter consist of a ceramic beeswax style honeycomb.   This honeycomb is coated with platinum-iridium catalyst.   The exhaust system gases cause the catalytic converter to reach extremely high temperatures.   As the carbon monoxide enters the chamber of the catalytic converter it is oxidized.   In 1996 automobile manufactures in the US were required to add a sensor known as the down stream O2 sensor. The purpose of this sensor is to monitor the exhaust gas and insure it is being oxidized to an acceptable level.