Help solving P0420 DTC on 2010 Honda Accord EX

Streamwood IL

Description

Hi. I have a P0420 DTC on a 2010 Honda Accord EX with 210k miles that I need to resolve to pass emissions testing. I just started doing my own work on the car and there is still much I do not know but I've done suspension work on the car and can probably replace the cat on my own. However, I need help identifying the root cause of the P0420 rather than blindly replacing the cat. The car does burn oil so that might be the issue. Any mechanics doing extra work on the side interested?