I have a 2015 XLT SCREW with the 2.7l Ecoboost with 67k miles and had my check engine light come on last week and the code is P0420. Ive done some research and it seems that it could and probably is a Cat thats gone bad. I cleared the check engine light, but it came back on 24 hours later. Could it be something else? I bought the truck 2 years ago Certified Pre Owned and purchased the extended warranty they pushed on me which ive used twice before this to fix an oil leak and a bad evaporator respectively. Would a bad catalytic converter be covered under any sort of warranty? I just dropped it off at the dealership this morning and im still waiting to hear the troubleshooting cause of error

 

Catalytic converter is covered under 8 year/80k mile emissions warranty.

Pretty good source of information on the code here:

https://www.fixdapp.com/blog/p0420-ford/