I have a 2020 JLUR with the 3.6. When I got my Tazer mini I updated it (11.1.5) before using it. It would not change my tire size, no matter what I changed it to. I sent it back to Zautomotive, and they sent another one. Same result. I rolled the firmware back to 11.1.4 and it works fine. I dont know what is up with 11.1.5 and the 2020.thanks because I've yet to get it change
I also bought an AEV procal snap, it worked fine to change tire size.
I went back to the Tazer because I have the front camera. I have since updated it to 11.1.8, but haven't monkeyed with the tire size settings, so I dont know if it will have any effect.
Try 11.1.4 with your diesel.