The last few days my truck feels like it has been surging when its in 4th and 5th gears when im on the gas. The engine light also came on so I got these 2 codes from OnStar ( P0401 and P0404 )...the guy said they were a powertrain module code.


Does anyone know what these 2 codes are?


Im not sure if the engine light came on because of my exhaust I put on ( mbrp system from the turbo back w/o a muffler) I heard the llys were throwing codes because of no cat.


I also installed a juice/attitude on my truck and ran it on level 3 for a few days b4 i dropped it back down to level 1. could this be a cause as well.....thakn you...Brian

Are you running the LLY?


IIRC, those two codes are the EGR related ones the guys are getting on some of the LLY's with the CAT's removed...http://www.dieselplace.com/forum/smileys/Ermm.gif

Yes I have the LLY. Thanks for the responce