Dpf is getting clogged. / def is contaminated or bad.

Mileage?
Driving % city vs highway?

I recommend hoping on highway and get it nice and hot 50 miles minimum then do some hard acceleration to blow it out

I use liqui moly dpf cleaner every 15k miles too

 

I thought pouring any def cleaner into drf tank was bad

 

Archoil has AR6400-D and Power Service just came out with Diesel Injector & DPF Fush fuel additive that is supposed to help clean out the DPF Filter. The Power Service is currently hard to find but both are available on Amazon if you want to try them out.

You could force a manual regen but you may need a mechanic with a diagnostic tool to do that.

 

I bought the archoil kit. Im on to the 6500 now still same.. I did my Manual regen with my cts 3 yesterday