I owned the first generation of the 1500 duramax and loved it. It wasn't my daily driver, so I kept getting a check engine light. My guess is and from what the dealership told me, is that I didn't drive it enough to have the soot burn off. I don't currently own the truck anymore, but I am thinking of getting another one after my lease ends. My question is, how often and how long does the engine have to run for the system to do its thing? One service tech told me to turn it on daily for and let it run for about 20 minutes. Any info would be greatly appreciated.