Perhaps see this discussion for OE replacement parts https://www.matthewsvolvosite.com/forums/viewtopic.php?t=86230 Look first for small holes in the cat itself, where the bracket is welded to the cat I bought a $250 downflex and cat for my 2003 NA off Ebay. These came prewelded but as I expected, t...

Even if you don't have the sunroof, may also want to slide a hand under under the front pass carpet, careful because it tears quite easily. Leaks may come from the cabin blower, cabin air filter cover, AC drain, etc I would not recommend the following if you have exhaust leaks, or if the trunk batte...

P0420 does not mean the catalytic converter is defective. It means the cat is not cleaning up as well as it should. This could be due to a lot of things that mess up the Air/Fuel ratio. It rarely is a defective catalytic converter. ECM-4801 ( P0420 ) Three-way catalytic converter (TWC) efficiency. C...

Hey the code didn't come back; it may not! I'd watch it for a while longer as you continue to diagnose. Good job looking at the O2 sensors. How old are they? Could the downstream sensor be shot? You'll want to check carefully for exhaust leaks too. Given the age of the car these are both suspect fai...