i get the blinking lights and code at start up. turn the key to on posistion and most of the time it will be blinking with that code.. On occasion after i clear it then been driving a while run in to a store come back out and it will start with out it.. what i have done. and prob didn't need to but it was easy .. i dropped the valve body and removed that Solenoid related to the code.. Its not shorted i get 5.5 ohms and i applied low voltage to it and solenoid activates. no short to ground from the TC to the harness plug at the tranny and no short to ground at the valve body harness. will double check this now that i have it back together.. continuity from pins on harness at TCU to tranny connector all good.. I have read some about voltage.. battery is 2 months old just got this truck a week ago kid put this battery in it.. gets 12.3-12.9 with vehicle off.. running about 14.1 give or take some.. soon i put truck on charger for a little bit turned key still blinking lights.. cleared it and turned off then back on and blinking lights.. i felt i should be getting more out of the alternator but again even after charging still happens... I'm lost now.. should i just replace the solenoid or alternator.. idk or is it a bad TCU? if you replace the TCU can you just swap or need dealer to do something to it?

any ideas

 

So I found a whole valve body from a 22. Solenoids and all. So for rating purposes. I just simply plugged in the 7 pin plug from the replacement valve body powered the truck on and still get the same code....... Cleared it and re powered again same code. Then for the hell of it I unplugged 7pin connector powered it on and a bunch of codes. But no p0748. Lol. Plugged back in to tranny and back to the p0748. I also checked voltage coming out of 7pin connector and was getting pretty much 5v from every pin. Gonna double check that in the morning. Any ideas anyone ?