New TCU is in. Truck would be in limp if it would start. The M&S lights are blinking. No gear indication. Windows, lights, climate control all work. When I push the brake the shifter interlock allows the shifter to be moved with no LCD indication and no other change.

 

This morning getting ready to reinstall I found a large gauge black wire with no home. It is on th RH side under the BCU, ECU, SLABS area. I thought it might belong to the header on the side but none were missing from there. I have searched for its home with no luck. I will keep looking.

 

cut all the tape off of the wires so you can follow that black wire to its home. i dont think that is the problem though because why would sinking your truck magically unhook a wire? so the shifter is moving and is the transmission going into gear? obviously you can't drive but you shoudl feel it go into neutral etc. im conviced there is a problem with the TCU communicating with the ECU. I dont think the TCU is letting the ECU know the truck is in park which is why it wont start. I'm not sure if the replacement TCU needs to be flashed by a T4 to be able to communicate with the ECU or not. maybe one of the techs can chime in. i would try and clean up the old one and stick it back in. did the truck run when you pulled it out of the water or did it die in the water? did you check the ground in the engine bay?

 

I did check the ground in the engine bay. The truck never died, drove home and the next day until it went into limp. Got home limping and the next day the truck would go back and fourth between being able to go into reverse and not. Then no start. Read on here about the TCU being under the seat and now I am here. I will keep cleaning old one. It has alot of corrosion and a transistor or something is actually rusting.

 

WOW! That battle is over. It was the XYZ position. It was the last thing to get reinstalled and nothing. I stepped on the brake to release the shifter and started running through and noticed random gear blips on the screen that would just go away. I stopped on N and then it went away. A little more push and it stayed on. Turned the key and BOOM! Got my buddy to spot the P and got back underneath, locked it down and good to go. Go get all them fluids flushed and then on through major maintenance. Thanks guys! You rock!

 

Lmao...... I thought you said the display want showing anything, didn't think to tell u to check the in between positions. That's what happens when the cable is not bolted in correctly to the xyz. There is a specific tool the dealer uses to align it. I actually never got mine perfect everything worked except neutral which was in between reverse and neutral was a real PITA to shift to low. Glad you got it figured out. Now get better door seals and don't ever sink the truck again