I have a 07 Duramax with 6 speed Allyson transmission. While pulling a trailer on the interstate my speedometer started jumping and abs and brake light came on followed by service brake system message then lost speedometer completely. Next was loss of rpm gauge, turn signals, radio and ac quit cooling. When I pulled over to check the truck I couldn't find anything visually wrong. No issues cranking the truck and engine sounded normal but transmission is stuck in first gear and will not shift manually but goes into reverse without a problem. It keeps dropping into neutral from first gear with message on dash indicating 'shift range inhibited'. Throwing codes po722 and po107.
Any help would be appreciated.
Any help would be appreciated.