My truck has had the p0420 code since I started driving it about a year ago. I got my 4R from my parents and apparently the CEL has been on and throwing that code for 5+ years…
The car runs great which I guess is why it wasn’t addressed earlier. After that amount of time I feel like I’d know if it was something serious, but I’m definitely checking out what could be causing the code ASAP now, just for the peace of mind