I have a headscratching toughy;04 Silverado

[hugger6933]

Extended cab 2wd 5.3 auto. I bought the truck it was hit light in the front[ front bumper and grill one headlight, but all the cooling was good as well as the radiator support. It was also hit down the right side I replaced the right door second door and bedskin. I got it out to drive it had no low and overdrive. Codes 740 tcc malfunction, 753 shift solenoid A, 758 Shift solenoid B, 785 shift timing and 2761 TTC pressure solenoid open. Well I carried it to a guy and he said he thought it was all doing what it was supposed to do but the trans was a fresh rebuild and it needed a wiring harness for the valve body in the pan. I ordered one put it on no change. I carried it to the biggest dealer in the state a 100 mile drive for me but when I have a big problem they always come through. Well I left it with them they called the next day and said a sprag was broke in the trans. I said no 4 codes it had to be wires. no they said it was a hard part fail and for $1900 they would pull it and fix it [just that one part]. I said no thanks I have three trucks at home the same model for salvage . I brought it home put another trans in it. Guess what? Same thing. I kinda wasn't surprised so then I said it must be some mashed wires behind the motor going to the trans valve body plug.my "mechanic" kept saying it has to be the computer . I told him it will never run if you put another on it cause it is vin locked and I can't reprogram here. Change the wiring harness and I think our problems will go away.Well guess what? the harness is off a 03 not a 04 [all I read showed they were the same] now it runs worse than poop and has 11 codes including the 4 for the trans. So now I have to change the harness back to put the other back on. Any body got an idea? Help a brotha out !!!PLEASE!!!!I have missed about 4 sales on this truck because of the problems and people wanting it but I just couldn't talk about it until it was ready.Please again. Jim

[68C15]

Bent pin at trans connector?
Loose or missing ground?
Use a 4064 heD light as a test light and see if grounds are ok. One side you hook up to battery, the other to ground pin at trans with harness unplugged

[hugger6933]

All been changed, First changed the valve body wiring,then the trans, then the engine trans wiring harness. Can you see why I'm out of ideas? I also think this is the reason I got the truck. The last owner had this happen to them had it worked on [trans rebuilt] and when it came back the same way, they brushed a bridge abutment with it to let the insurance take care of them. Good thing my hair is kept cut short or I'd be pulling it out after this one.I told my dad when I was pulling it into the shop I wanted to junk it out. He said are you crazy it is way to nice and clean. I said nice truck make nice salvage. Jim

[lowridergmc]

do you have 12v to the trans?i have seen ignition switches and under hood fuse blocks cause this.

[hugger6933]

I had considered the ignition SW. But not the UBEC. Thanks. Jim

[gmclowsierra]

follow the trouble tree for the codes. they are very good. follow them step for step and do not skip any.