Thread: p0420 codes... common??

is the cat efficiency code a real common gm problem? any fixes? would a high flow cat/02 emmulator fix the problem and still pass I/M?

car is a grand prix 3.8L S/C

I have had it come and go since I got my 03 GT @ 75,000. I have tried 3 or 4 universal cat's after the factory one started to plug. I ignore mine, each time the cat was covered under warranty so I am not out much. I do have a $45 scanner I will check codes every once in a while to be sure nothing else has shown up.