The 327 worked great from CA to Texas. Next AM started duramax van and gages were acting goofy and the AC wasn’t working. Disconnected 327 and almost everything was back to normal except the van thought the DEF was low when in reality the DEF tank was almost full. When the van thinks it is out of DEF, it goes into LIMP mode, 5 MPH max speed. LIMP mode wold initiate in 600 miles and we were on a tight deadline to get to GA. We found a Chevy dealer on a Saturday AM in Odeasa TX who reprogrammed the DEF fluid level for ONLY 350. Had this happened on a Sunday when dealers are closed we would have been SOL. Moral of the story… unless you are having problems or don’t need to rely on your vehicle, don’t install one of these units. It seamed like a great idea, but this is a business vehicle that must work.