Ok well I have an 2005 dodge magnum RT and im having a bad no start issue. It all started after i used an older model hypertech tuner on my car. I flashed a premium tune on it every thing ran great. Than i changed it to a regular tune. The car drove for about a minute than it died. The code im getting is an u0100. Some times it may start than other times not but when it does start it dies after one minute. I think my ECU is fried but im not sure. Id like to not take it to the dealer because im scared of other issue's the dealer may cause. Iv not took my car to a shop outside of tires & exhaust in over 10 years. Im in Fort Smith Arkansas btw if that matters at all. Any and all help is needed thanks ahead of time . Oh and when the key is in the on position it clicks from the throttle body and relays. i have a couple videos to show whats going on.
Battery is good, starter is good and alt is good


https://video-dfw1-1.xx.fbcdn.net/hv...d6&oe=55E6C2DC

 

U0100-LOST COMMUNICATION WITH ECM/PCM.
Sometimes this is caused by a bad/low voltage battery, but in your case I think that when you reprogrammed back to stock your tune was toasted. I have heard of issues where guys that performance tuned their cars and then went to a regular tune ended up with a messed up tune in that the tuner did not tune properly and the car would not run, just like the issue you are having. I also have read that a lot of guys had not have good luck with Hypertech with LX platform cars. Most seem to think that Diablo is the way to go.
You might want to check your fuses to make sure none are blown, check the battery voltage and alternator output (in case it is low voltage related), disconnect the battery and let it sit for awhile then reconnect the battery and see if the tune will reset. If all else fails you may have to take it to a shop/dealer to get a stock tune reloaded.
Good luck and I bet one of the LX gurus here will be chiming in later with more ideas.