Catalytic converter check engine light?

[cr2256]

I just finished a trip from Ohio to Georgia through the west Virginia and Virginia mountains with a 10k lbs travel trailer.  Truck handled the mountains great but as I got close to home I got a check engine light which translates to P0421 error.  I'll be taking to the dealer but has anyone had this at around 3k miles?  Looks like its related to catalytic converter.

 

I have a 2020 2500 Duramax.

 

Let me know!

[Colossus]

Let us know.  First I've heard of it on here. 

[Kenneths77]

I had a tree fall on my black 2020 High Country  so I traded it in for a white demo 2020 High country as they were servicing it for me to take home they noticed the check engine light was on. Turns out they have to replace the DPF. Waiting for it to come in now.

[cr2256]

Taking it tomorrow.  I'll update once they diagnose it.