Circuit Description

In order to control emissions of hydrocarbons (HC), carbon monoxide (CO) and oxides of nitrogen (NOx), a TWC is used. Catalyst within converter promotes a chemical reaction that oxidizes HC and CO present in exhaust gases. Oxidation process converts HC and CO into harmless water vapor and carbon dioxide (CO2). Catalyst also reduces NOx by converting it to nitrogen. PCM monitors this process using HO2S (sensor 1) and HO2S (sensor 2). PCM compares the difference between the 2 reading to determine oxygen storage capacity of the catalyst.