Hi all, I'm new to the forums and seeking advice on a no start, likely electrical issue. I have a 1996 7.2L E350 shuttle bus that lost all power while driving on the freeway on me last week. I've since had it towed to my house and have ruled out any sort of battery issue. The bus has full accessory power including headlights, stereo, etc. However, when I go to turn to start there's no response from the vehicle except some misc lights turning on while holding key in start position (e.g. abs). The vehicle has some funky wiring from past owners with bundled up cords in electrical tape that are difficult to track down so unsure how feasible it will be for me to troubleshoot this with my limited knowledge. That said, I figure I'd try this post in case anyone has some good idea about what might be going on and can save me the tow to a mechanic.

Video trying to start the vehicle:
https://drive.google.com/file/d/1NAU...ew?usp=sharing

Also, the RPM control unit (sorry not sure what it's called) is now showing "CErr" since the issue started, never saw this before.