I have a 2011 Buick LaCrosse with a 3.6L. It is automatic and has about 86k miles on it. My check engine light came on yesterday, and it threw a P0420 code. It ran fine yesterday, noticed it was a little sluggish for about 5 minutes and drove it again today and it seemed to be fine. I took it to the repair shop and he said it needs a new catalytic converter without even looking at the car. Is it this or could it be a 02 sensor I keep seeing that could be the possible culprit? Any insight would be greatly appreciated.
P0420 does not always mean the catalytic converter is the root cause. You have to do the proper diagnostics and confirm (or rule out) that it is the catalytic converter. For that start here:
https://carkiller.com/scottykilmer/postid/82224/
