Have 2004 Duramax 6.6l with 147K miles, Allison tranny. Yesterday getting onto the highway an engine light came on and engine would not go over 2000 rpm. Pulled off, put it in neutral, same rpm limit. Creeped back to the shop under 20 mph. Hour later, started the engine, seemed to rev up over 2000 rpm just fine. Did not attempt to drive it. Taking it to the shop this morning. Any idea what might be causing this? Thanks

 

it is in limp mode for some reason... it will say why when they read the codes...if its really cold could be geling or your fuel filter could put it in limp

 

Yep, sounds like a limp to me as well. If the trans was cold, and you were accelerating fast (like getting on the highway), that can cause it.

Its just the Trans's way of protecting itself from breaking something. It limits the amount of power via TCm/ECM communication.

Lets see what codes come up

 

Any updates??

 

Any luck??

 

sounds like an engine limp, where it wont go over 2k rpms

what are the codes?

 

Bump!!!

 

Closing due to a one time post and lack of activity.