Catalyst And Exhaust System: Overview
The catalytic converter and exhaust systems work together to control the release of harmful engine exhaust emissions into the atmosphere. The engine exhaust gas consists mainly of nitrogen (N), carbon dioxide (CO2 ) and water vapor (H 2 O). However, it also contains carbon monoxide (CO), oxides of nitrogen (NO x ), hydrogen (H), and various unburned hydrocarbons (HCs). The major air pollutants of CO, NO x , and HCs, and their emission into the atmosphere must be controlled.
The exhaust system generally consists of an exhaust manifold, front exhaust pipe, front universal heated oxygen sensor (HO2S), rear exhaust pipe, rear HO2S, a muffler and an exhaust tailpipe. The catalytic converter is installed between the front and rear exhaust pipes. Catalytic converter efficiency is monitored by the on board diagnostic (OBD) system strategy in the PCM. For specific OBD catalyst monitor information, refer to the CATALYST EFFICIENCY MONITOR .
The hybrid vehicle is a partial zero emission vehicle (PZEV) equipped with two sensors that provide input to the PCM. The first sensor in the exhaust stream before the catalyst is the universal HO2S and is used for primary fuel control. The second sensor in the exhaust stream after the catalyst is the HO2S and is used to monitor the light off catalyst.