Mine did it for some time as well as a guy I work with. Both trucks are Job 1's. Both were eventually diagnosed with a bad sensor on the DPF/DOC pipe assembly. It took the dealer 3 times to finally find mine. It was actually in the middle of a regen when I pulled into the dealer for last time. I drove it inside the service bay area, left it in drive, set the parking brake and let it regen it's little heart out and fill that place with smoke....

My truck was also eventually diagnosed with a leaky turbo so that might have been it too...