Long story short i purchased a 2018 10r80 from auction. i payed about 9k for it. The only issue is that it did not come with any keys at all. When i tried to get one programmed by the lock smith, he couldn’t communicate with the pcm to program it. Upon further inspection i ran into a bunch of ground wires (7 wires to be exact) that ran into the pcm harness for the “ vehicle” section. As you may know the pcm has Engine, Transmission & Vehicle inputs. Anyway, I spliced the grounds back and they are making contact already & there was still no communication so i searched further and found more wires which is the bundle that goes into the fuse box. i also spliced those & they are making contact now. My question is, did my pcm get electrical damage due to the bad ground? I am replacing the wire harness but i also wanna make sure my pcm is good before i buy another one, the car also freaks out and turns on the hazards when i open the door and it also flashes the dome interior lights alongside the hazards. i’m also replacing the BCM to make sure everything is intact.


I will provide everything below! maybe you guys can give me an input on the electrical side of this.

This harness runs into the fuse box.

these are the ground wires that run into the “ vehicle “ input of the pcm.

this is the pcm opened up, i didn’t see anything that could indicate that it’s fried. could there be damage without me seeing? being that the impact was on the side that the pcm is could it have shifted something?

 

Your best bet at this point is to go to an Auto Electric shop and have a full electrical diagnostics done. They can test all of the circuityr. Yes it will cost a couple hundred bucks but, you will have a better idea or possibly know exactly what is wrong. It only takes one loose or bad wire to haev a communication problem. The money spent will be worth it saving you time and who knows how much in parts thrown at it.

A new engine wire harness is Several Hundreds if not around a grand. A new or used PCM, no idea but i wouldn't bother to look at that until you know for certain the wiring issue is not the problem.

 

Yes, the harness is $550 Brand new Oem. I found a used pcm for $300 & $150 to program it. Might just tow it to the body shop and have them deal with it, have them include it in the bill.

I also got codes for the bcm getting low input, the start button sensor faulty code & when i open the door the hazards turn on and the dome light flash along with the hazards. So could that be out too?

 

A bad wire harness and unknown sensor and communication damage/issue can cause seemingly unrelated systems to flip out. That's what sucks about newer cars, everything is interconnected and if you don't have the tools or experience to track down the root cause, you'll be chasing your tail and wasting a lot of money and time.

Not sure a body shop can handle it, they'll probably source it out to an Auto Electric Shop. Skip the middle man and time waste, just go right to the Auto Electric shop.