I have a 2012 KW T660. I bought it with a def problem. When I took it to the shop it was the nox sensor and the dash showed red engine light, yellow engine light, and a message " LOW DIESEL EXHAUST FLUID". Nothing showed on the def gauge. Fixed it and it drove for a week before having to take it to the shop again. This time red and yellow light appeared. Also the same message and now the red blinking light on the def gauge is on. First the red blinking light shows up and its at a full tank with the message LOW DEF FLUID and after an hour it brings the truck down to 5 MPH. we cleaned the dpf filter but still it did not help it.