I was having problems with the duramax jumping into limp mode when pulling the 5er up a mountain. Seems the mini max chip calabration on the turbo temp. was off several 100 degrees, this caused the computer to think the turbo was overheated when it actually wasn't. So thinking it was overheated caused the turbo to defuel which throws it into limp mode. We recalabrated the mini max to the correct setting. Hope this solves the problem. I still feel the chip is the way to go, what I have saved in fuel far out weights it's cost and this the first problem it has caused us. Thanks for all the help, many of your comments put us on the trail of finding the problem.
The truck in questions is a 2008 2500 4WD Crew Cab pulling a Monte Vista 31.5 with a weight of around 10,000lbs. The truck as 55K on it, its been running for over a year with the Mini maxx set on Mild at all times with no trouble. I also have a 75gal acc. tank that I generally fill to about 50 gals. Gets service every 5000 with new fuel filter. It had gone over 1000 miles on this trip before the Limp mode problem, that didn't develope until we reach the Mountains. Reguardless of somes doughts, the chip does make a big difference in fuel use, I check it manually every two or three tanks, the trucks computer on fuel use is off several gal. When I figure out what causing the problem I will post the solution. I am going to upgrade the chip tomorrow, also will find out what GM tech has to say about the codes the service Mec. is sending them. The first thing I did when it went into Lemp Mode the first time was replace the fuel filter. I have been fueling from here to the keys and back, thought I may have pick-up some bad fuel.
The reason I chipped was to improve fuel economy, I get not pulling, running at 65 MPH 23 miles to the gallon, pulling I get between 13 and 14 at the same speed. Running 40 or 50 K year this adds up to more than the price of a transmission. However, I am going to look into upgrades. Thanks for the advice. JRP
Pulling my 5th wheel trough the mountains I have had it jump into limp mode several times. I am using a H&S mimi maxx chip, I can clear in with the diagnostics on it, I think it will also clear if I turn the engine off for 60 sec and restart. Is their anyway to prevent this from happening? I was told the computer though the transmission slipped and through it into limp mode? Any advice would be appricated.