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International Automotive Technicians Network
Re: '01 Prizm/Corolla the dreaded P0420 code ?
Posted to Technical Discussion Forum on 3/3/2011

By graphing the o2 sensors your are just duplicating what the pcm has already confirmed, (the O2 sensors are switching at the same/near the same rate) Check for air leaks, and PCM updates, or TSB's concerning the code. but the Pcm is pretty smart, and double c... Login to read more.