Circuit Description

In order to control emissions of hydrocarbons (HC), carbon monoxide (CO) and oxides of nitrogen (NOx), a Three-Way Catalytic (TWC) converter 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 No. 1 and No. 2. PCM compares difference between the 2 readings to determine oxygen storage capacity of the catalyst.