Hello I have read some of the comments concerning the Duramax Diesel. I will start by saying that I work for an EMS service We have 4 of the express cutaway vans 2 are the 4500 series and 2 are the 3500 series. the 2 4500 have given no problems at all They have been great they are 08 and 09 models. We have 2 2012 model 3500's and one has done good while the other has been nothing but a pain in my side. it all started at 38,600 miles. A message light came on telling us that the vehicle was cleaning the exhaust and to keep driving until it went out. It never went out after about 50 miles of driving. Took to dealer and it was still under warranty. They told us it was the exhaust particulate filter and that warranty did not cover it due to it being a maintenance issue. Ok how do I maintain it. that filter was $1400 dollars. They did however manage to get it fixed with a warranty. the vehicle now has 52,000 miles on it and is in the shop for the 10th time for this same issue of the message coming on and telling us the vehicle is cleaning the exhaust drive until message goes off. Each time it has done this there is a different problem. the last 3 times we just kept driving it and the it suddenly went to reduce power mode and we could not get over 30 mph. stop on side of road shut it off runs good for about a minute then goes back to reduced power mode. It is in the shop now being looked at yet once again. Gm has fixed it a couple times but it throws a different code every time they look at it. I have heard that there are ways to take this DEF crap off the truck and not hurt it. Anyone know how that is done. Any ideas will be greatly appreciated