ISX in 2013 Pete 388 Regen required light

[JimT]

Any fault codes? Has it had a full EGR tune-up? Could be a clogged up sensor somewhere.

Unless I'm mistaken the "soot load" is calculated. I believe it's the differential pressure and the overall exhaust pressure/flow rate that are used to determine if a regen is needed. You could have an exhaust restriction somewhere, like the Decomp Tube or SCR can (crystallized DEF buildup or ash buildup). Could also have an exhaust leak somewhere throwing off sensor readings.

What does the regen history look like in Insite? That can tell you a lot about how the system is performing. Take a screen shot or picture and post it here.

What kinda miles on the truck? If it hasn't been done yet, the DPF is supposed to be removed and cleaned somewhere around the 400-500k mile mark to remove ash buildup and flow test it.

Engine rebuilt? Whats the oil consumption? Have you tried disconnecting the exhaust pipe to check for coolant, fuel or oil getting into the exhaust? While that's off you might want to run the engine and see what's actually coming out of the exhaust. If it's throwing a lot of smoke then that will clog up the filter quick.

Part of the EGR tune-up is to remove the DPF Doser Injector to inspect and clean the soot/carbon buildup. Also wanna check the EGR system and Air Intake system for proper function and leaks. Did I mention doing an EGR tune-up?

A lot more things to check, but I'd start there. Most likely you will find something that either fixes the problem or points you in the right direction.