2018 xc90 p0420 code ?
 

New to forum, so Hi. I purchased a 2018 XC90 2.0 with 139K but, has a crate motor installed with less than 100k on vehicle. This last summer it started having a CEL P0420. Sometimes it would clear itself, or i would have to clear it with scanner. I have used cataclean several times with no help. When I first got the SUV I noticed that the tailpipes were very black on the inside. At the time, premium was very expensive, and had read on other forums that you could run regular gas. (I have gone back to premium)
Fast forward to today, I have been unable to clear the code, not sure if the cat is plugged. What should the O2 sensors read (voltage and ohms)
The last time the light came on, it was shortly after i started driving. Not sure if there is an exhaust leak or not, doesn’t sound like.
I guess my question is this: Is the cat need replacement due to soot in tailpipe? Need to verify that sensors are working properly. With not that money miles on motor, I wouldn’t think there would be underlying issues with engine??