Hello, need some information to help with my sons truck. He was helping jump a friends car and misplaced the jumper cable on wrong port and has now caused the entire computer system to shutdown. The truck was towed to our house and my husband has checked every fuse and researched all that he can. He has ordered a part from GM hoping it is the fix, but I think it may be more complicated. Can you provide any insight? He is able to unlock the truck with the key fob and has power to the left side of vehicle.

Thanks,
Lynnette Thompson
'19 GMC Sierra 4x4 V8 5.3

What lights in the cluster with key on engine off.

Nothing. Total blackness.

No lights yet the fob works. What is the state of the battery?

My son says the dash doesn't work, the horn doesn't work, exterior lights work except for right headlight, yet turn signals work. We believe battery is ok. Interior truck lights work as well.

Sounds like the BCM or other modules may have been zapped.
Need to put a GOOD scan tool on it and see what all modules can communicate if any.