DTC P0420: : TWC System - Low Efficiency - Bank 1 & DTC P0430: TWC System - Low Efficiency - Bank 2: Description

The engine systems uses a 3-way catalytic converter (TWC) to control emissions of Hydrocarbons (HC), Carbon Monoxide (CO), and Oxides Of Nitrogen (NOx). The catalyst within the TWC promotes a chemical reaction, which oxidizes the HC and CO that are present in the exhaust system. This reaction converts these chemicals into harmless water vapor and carbon dioxide. The catalyst also reduces the NOx which converts into nitrogen. The Powertrain Control Module (PCM) monitors this process using Heated Oxygen Sensors (HO2S) bank 1 sensor 2 and HO2S bank 2 sensor 2, which are located in the exhaust stream past the TWC. These sensors are referred to as catalyst monitor sensors. The catalyst monitor sensors produce an output signal which indicates the oxygen storage capacity of the catalyst. This determines the catalysts ability to effectively convert the exhaust emissions. If the catalyst is functioning correctly, the catalyst monitor signals will be far less active than that of the signals which are produced by the fuel control HO2S 1 bank 1 and fuel control HO2S bank 2. This indicates that the TWC oxygen storage capacity is at an acceptable threshold. When the response time of the catalyst monitors are close to that of the fuel control sensors, the ability of the catalyst to store oxygen is considered to be below an acceptable threshold. If the PCM detects this condition, DTC P0420 catalyst low efficiency for bank 1 or DTC P0430 catalyst low efficiency for bank 2 sets.