My 1996 6.5L K3500 goes into limp mode between 70-80mph. ses light come on sometimes but I have no communication with my PCM. If I restart the truck i'm good till I get to 70-80mph again. I checked all the wires at the ALDL port an I have all my hots and grounds. What should I check next?

 

how much boost are you pushing? my old 6.5 would go into limp mode before i put a chip in it.

 

I'm not sure how much boost it is. I'm running the turbo master kit from Heath diesel and the spring measures 2". Should I tighten it or loosen it?

 

get a chip. i think your pushing to much boost for the stock computer. mine did the same thing. or let off the boost some. But the computer says its running to much and things the waste gate is stuck closed, and that makes it go into limp mode.

 

Okay thanks I turned the boost down now its not going into limp mode it must have been making the truck run to lean which caused it to go into limp mode. I guess the problem with the scanner not reading the computer is a different issue.