CODE: PO 421 on 2000 Mitsubishi Eclipse

I got a code #421 warm up catalyst below threshold (BANK 1) CAN SOMEONE TELL ME WHAT THAT IS

by in Hanover, PA on May 12, 2011
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1 answer
ANSWER by , May 12, 2011
It means it is likely that you have a catalytic converter that has stopped being effective and needs replaced. But before you do that -- verify the operation by testing it. The efficiency of a catalytic converter is measured by sensors before and after it. A problem could exist there.