Upper cat is in the manifold. It is not likely they replaced that...and it is probably the source of you P0420. Pretty sure that is the cause on mom's AWD as we replaced the rest of the exhaust system. My mechanic says both converters are dead on my 2005 AWD. ( https://www.ebay.com/itm/Manifold-con...

My mechanic says both converters are dead on my 2005 AWD. ( https://www.ebay.com/itm/Manifold-converter-Toyota-Matrix-AWD-only-2003-2004-2005-2006-Direct-fit/122531534541?fits=Year%3A2005%7CModel%3AMatrix&hash=item1c8772d6cd:g:s3gAAOSwZ4dZMwNt) (https://www.ebay.com/itm/Fits-Toyota-Matrix-Pontia...

I am in PA. Is welding in a new cat a job that a regular mechanic does or are there specialized shops that deal with all things exhaust / muffler related?

Update: I watched the O2 sensors while driving and they seem to be behaving properly. Upstream sensor is jumping around a lot while downstream is staying around 0.5, oscillating slowly up and down a little, and reacting to throttle changes. I cleaned the MAF sensor and PCV valve. Also decided to cha...

Thanks for the tip on the temperature of the cat. I'll look into that. Follow up question on the catalytic converter; I read that the AWD has two cats, one just below the upstream O2 sensor and then the second one under the car. Does the first, upper cat ever go bad and could that be a possible caus...

Hey everybody, I've got a question for the vibe community. Background: I bought a 2005 AWD vibe 2.5 years ago with 75,000 miles on it. The guy I bought it from had replaced the catalytic converter with a new Walker ( not great, I know) one at 70,000 miles. A few months after I bought it, the P0420 l...