Well it happened today. My 2004.5 lly Dually was running at 75 mph and when I went to pass another car it coughed and sputtered and now 65 mph is topps and it will not go over 2000rpm's.


Does anyone have a idea of what is wrong before I take it to the Dealer. My code reader says NO Codes. I have a Bully Pup and it is not loaded in it now and still the same problem.

I think you might be in high idle (warm up or PTO) mode ask one of the techs about it I belive it came preprogramed into the lly's but not the earlier models. ask the tech about the high idle setting. hope this was useful.

Thanks for the Info. I will check when it goes in tomorrow.


This is my Third Duramax and I have been Lucky that I haven't had any problems with them. In Fact my 2001 never went back to the Dealer for anything in 97000 miles. My 2003 went back a couple of times for Little Things. But my 2004.5 Dually is another story. I just can't seem to ween it from the Dealership. I starting to wish I had never traded. http://www.dieselplace.com/forum/smileys/smiley7.gif

It has to do with the fuel pressure not being maintained after boost. Common on the LLY section. Mine does it too. Happens with Chip and open exhaust most. Newest ECU flash from GM dealer said to fix it. I'm getting mine done next.