I posted a few times asking questions so I will try to be as brief as possible. I had a 4L60 in my truck and my nitrous kit was wired into the ignition zero fuse in the drivers fuse panel. The nitrous fuse blew, I replaced it twice and then my transmission went into limp mode a few days later on its own. I had not used the spray.I changed all the solenoids as I had a few codes pertaining to solenoids, P0785, P0753,p0758 iirc. I swapped a Pcm and have ohmed out all the wires to the transmission from the PCM and checked power. I have now swapped to a 4L80. I am having the same issue. Upon engine start (after sitting off for more than five minutes) I have first, second, third then it stays in third unless I manually shift into second gear. I have no lockup,no fourth gear. Only third gear. Anybody have any recommendations or ideas? Any help would be greatly appreciated. I don't know if the nitrous system being wired into the ignition zero fuse has anything to do with it.The kit is now disconnected. Thank you

 

We hooked up a known working solenoid pack. 3-2 shift solenoid wire between pcm and trans broken. Finally we are getting somewhere. Now to find and repair it.

 

Officially found the electrical transmission problem. One day I fired up my truck and chopped a field mouse in the cooling fan. This is what he did to me, chewed up wires and transmission hell. His nest was under the fuse box. Thank you to my best friend Greg Lovell @antivenomefi for all the help. I wanted to leave this here to possibly save someone the headache I've had for so long. Brand new 4l80 and brand new FTI 4000 will be on the road hopefully sat! Finally excited about my wheels again.