Quote Originally Posted by green91
Unless its completely blown out, you can't look at a catalytic converter and tell if its bad. A fuel trim issue will set a completely different code.. usually a p0171 if its really lean.
Correct even a small hole that the human eye cant see can trigger this code

PO420 Means You need a cat, it will still run 100% but in order to pass emissons and get the light off you will need it replaced!