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Anytime you have a P0420 code or a P0430 code this is not a sensor malfunction. Do not waste your money on air fuel ratio sensors or oxygen sensors. They are doing their job correctly otherwise these codes would not even set. Anytime you have either one of these codes for bank one or bank two it is a converter failure. The catalyst efficiency is deteriorated and the computer has detected this by monitoring both AFR sensor and rear oxygen sensors. In some cases there are some computer updates available on certain models to help address some of these failures. However 99.9% of the time you have to replace both converters for both banks. If you do not live in a state that requires emissions inspections order to renew your license plate you can just ignore this code if you don't mind looking at the check engine light. This will have no effect on the engine performance with the exception of possibly one or 2 miles per gallon fuel differential.