P0420 DTC Code - Catalyst System Efficiency Below ...
2011-7-1u2002·u2002Most cats do not go bad by themselves, something else is usually the cause. Ie: bad injector, bad spark plug, bad wires or coil pac, etc. Something that is causing gasoline to enter the CAT, without completely burning the fuel, will foul it. I am willing to bet there were or are other codes with your P0420.
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