T880 gauge question

[ADDRepair]

Hi all, first off let me say I would not post something unless I was out of options, and ready for the "paddling" lol.

That being said, I have a 2015 t880 ISX15. I had somebody remotely de-mandate it about a year agoo. everything, so far, SEEMS ok. My only issue is that the driver is insisting that he wants the def-level gauge to show full, instead of empty (its current state). I have tried the usual RLOC trick, to no avail. Is there any insight you could provide to correct this? I havent had a lot of these scenarios in front of me. Is this a CECU-based solution, or something else? I appreciate any insight, and am prepared for the duly deserved lambasting lol