DTC P0420: Catalyst System Low Efficiency - Bank 1; P0430: Catalyst System Low Efficiency - Bank 2: Description

A 3-way catalytic converter is used to maintain low emissions. Powertrain Control Module (PCM) monitors exhaust gases from converter using HO2S bank 1, sensor 2. Sensor is located in exhaust stream past 3-way catalytic converter. These sensors produce an output signal which indicates oxygen capacity of catalyst. This determines catalyst's ability to convert exhaust emissions effectively.

During normal operation, HO2S bank 1, sensor 2 signal will be far less active than that produced by HO2S bank 1, sensor 2. If a problem exists causing PCM to detect excessive HO2S bank 1, sensor 2 activity outside of an acceptable range for an extended period of time, PCM will set a DTC. This indicates that 3-way catalytic converter's oxygen storage capacity is less than acceptable range.