I have a 2007 5.9 it just started to Have problems.
It has erroe code P128D
it also had a one time P2509
The truck idles fine but when put into gear it ether dies or the rpm jumps up and the truck feels like it wants to run away almost like you are stepping on the gas with the breaks on.

I have done the following:
Check battery voltage
check all grounds
Take out the superchip programing and return to factory
taken power off batteries and left for 3 hrs

If i get the truck running it runs fine however i did have it die on me and it took a little while to get running again.
When it has the P128D error code the lights on the dash P N R D 2 are not lite up. it seams to be a transmission problem but i am not sure.

PLEASE PLEASE HELP

 

has nobody had this code?