How do I know if my DPF is full?

You can plug into it with DDDL and it’ll give you a % full. I do know when they are full you will get a check engine light and a code on the dash. The newer dashes will tell you. Since Detroit has made their recent change to their website, their troubleshooting doesn’t come up in Google searches any longer. But you can still google it and just by reading the headings that the DPF have reach service life.

Either way I’ve not been around one that had the code active for more than 24 hrs. So I’m not sure how long it can go. Usually when the light comes active, the driver calls and we make arrangements for the next day. Sometimes not getting the truck to the shop till the next morning.

 

If you have frequent regens, and the regen lasts only about 15 min, it's full

 

Right. And, honestly, at those miles, you're about due.

 

I belive theres an idiot lamp symbol that comes on looks like bacon frying on a rectangular pan.
I imagine theres restriction sensors within the air intakes. Restricted filter will effect the engines performance good luck!