07 lmm

[Curtis]

Hi folks,
New to this so bare with me. Looking for some
help. Just had my 07 LMM go into limp mode with a P0299 code. Truck is bone stock other than 6" lift and 35" tires and only 68k miles. I know it is a turbo underboost code. Drove about 50 miles in limp mode and turned engine off for approx 15 min. Started back up and still had engine light but ran normal and still is after 2 days. Any ideas would be appreciated. Also I went ahead and changed air filter just cause and i have cleared the code and havent seen it come back yet.

[mpdtune]

What tune are you running? sounds like a turbo with stuck VGT or maybe a Mass Air Sensor problem.

[Curtis]

No aftermarket tunes on this truck. It is bone stock since new. Havent had a problem since clearing code however I havent pulled a load yet either. It only has 68k miles and had a 16' lowboy with a kawasaki mule on it when it went into limp mode and threw the P0299 code. My mechanic thinks it might have been a glitch since not having any other issues with it

[cumminsDK]

The last 07 I worked on with that low of miles set codes because turbo vanes were rusted up from sitting, but it was a turbo boost control position not learned code

[Curtis]

The last 07 I worked on with that low of miles set codes because turbo vanes were rusted up from sitting, but it was a turbo boost control position not learned code

Well I bought it with 26k miles about 3 and half yrs ago. I have a company truck and mine sits in my shop so its not out in the weather. We do have very seasonal humid conditions here in the south. Guess we will see what happens in a few weeks when I put about 9k pounds behind it.

[tokymon]

you could also use the dvt in the scanner to manuall move the vgt vanes to see if they are sticking

[Curtis]

Thats a good idea.... If it throws another code then I will proceed with that process. I also plan on getting a tune and exhaust since the warranty is out which sucks because it only has 68k miles but 6 yrs old. Thanks for the input....

[StinkyDog]

Just a thought. With 35" tires your gearing will be CONSIDERABLY higher than stock. With the added pedal position (to move the big tires) and low RPM, could the truck simply not have enough drive pressure to spin the turbo? I know that underboost code can be kind of sensitive. The Duramax likes RPM (unlike the Cummins). Try running in a lower gear and see if that helps your problem.

Just thinking out loud.

[Boost]

Just a thought. With 35" tires your gearing will be CONSIDERABLY higher than stock. With the added pedal position (to move the big tires) and low RPM, could the truck simply not have enough drive pressure to spin the turbo? I know that underboost code can be kind of sensitive. The Duramax likes RPM (unlike the Cummins). Try running in a lower gear and see if that helps your problem.

Just thinking out loud.

This. :exactly:

[Curtis]

Very possible...never thought about that as i've never had that problem before. I had 37"s on it fo a while with no issues. However it hasnt had a problem since i changed the air filter and reset the code. The filter wasn't too bad but just changed it anyway. Guess we will see in a couple weeks when I tow out to west Texas about 7 hrs. Thanks for the reply.