JBChance

Posting on this because I had a similar issue. On the off chance you are watching this or also if someone is battling the same (thats how ended up here), I wanted to post what I found out. I have a 2017 Silverado 3500HD, 6.0L gas. My issue was caused by a short in the harness. Specifically for me, it was the trailer plug wiring. Because my truck is a salt truck, there is always chance for extra corrosion and so forth. The plug was put in aftermarket and the splices became compromised. The power circuit to the plug was shorting through and, I believe now, into the truck ground. You would think that would blow the fuse, but it did not. My truck would not go into reverse or shift, no tach/ speedo, and the OBD2 port was dead or couldn't communicate. In addition, weird goings on like the blower fan/ climate control would stay on with the truck off (and other things). When the episode occurred, the service trailer brake system warning went off directly prior, so I was lucky and started at the plug and discovered the short. From what I understand now, this scrambled the BCM/ ECM and created havoc. Once I corrected the short, nothing changed, until I reset the ECM by disconnecting the battery and letting the truck sit. I reconnected (ECM reset), and the truck operated normally. I did get the put the drivers window down and up promt on the info display indicating a reset. Sorry for the long post, but I know I was stumped for a day, so, if this could help someone, so be it. Cheers!