Hey everyone, I just bought a slightly high mileage Accord and when I purchased it, it had a check engine light on (P1157 - O2 sensor). I replaced it with an OEM sensor (Denso, I believe) and that code went away for about a day, then the CEL came back on the next day with a P0420 code, which from what I gather means the Catalytic Converter is not working properly or there's an exhaust leak. Is there any necessary reason to really replace the cat on an older high mileage vehicle aside from the fact that it may be giving off more pollution? In MI we do not have yearly inspections, but if there's a chance it'll damage the vehicle I may spring for one. Any thoughts? It seems to run perfectly fine. -knocks on wood- I've never had a Catalytic Converter go out on any of my vehicles, so I'm not very familiar with what I should do in this situation.