it is the message you get when the DPF filter is starting to clog. you need to get it cleaned or you will be dead on the side of the road. sounds like you may have used dome LSD instead of ULSD fuel, and that will clog the DPF faster than you think.
also your regen system may have a problem going into regen mode. you need to take care of this as soon as possible.
2006 gmc 3500 xcab lb, with the LBZ.
with air dog lift pump, race valve, egr delete, and efi reprogram, thanks to husker diesel.
84 gal fuel cap.34 main and a 50 gal aux transflo system.
20k curt 5th wheel, 20k goose neck.
still stock. 4x4. 430,000 miles and counting.
transporting new units from factory to ia. dealers and ship.
engine replaced at 404,000 mi with one with 118,000 miles.