I don't think it was in regen, or had just finished one bc the message wasnt displaying, but I had to have a sensor replaced and it had to be manually defends at the dealership bc it went into limp mode last Thursday, I pulled my camper about 200 miles after that and haven't driven much other than that, hoping its just left over soot from that, so I drove it pretty hard for a couple miles and it sorta cleared up, stopped doing it, but I had driven stop and go and allowed it to idle quite a bit today so I'm also wondering if it coulda just been a lil build up burning off????