I was heading to an appointment and when I arrived I turned off the car and the dashboard went to a solid white screen. Tried restarting and resetting everything to no avail. Later that day the dashboard went totally black. I called my dealership and they said to bring the car in. So the next morning I went out to the car and it was completely dead. I could not unlock the doors to get in, never the less start it. I later learned the workaround, but for this trip I had to call a tow truck to transport the car. At the dealership ship they confirmed the dashboard was dark and they found the 12V battery only measured 3.7 volts post-to-post. They jump started the car and starting cheeking for codes and found multiple low voltage codes were set in multiple modules. The tested the battery and found the battery tested fine. They also performed a 14V power module stress test, and it tested normal. Retested the 12V battery again and once again the battery tested good. Consulting with GM they then did a trans range control module software calibration update after learning one was available. I have have no idea what all this means, and the service reps had difficultly explaining it as well. I was not able to talk directly with the mechanic/technician. After all this the car was fine. The kept the car for another day periodically driving and checking but nothing new was found. An added bonus happened on the way to the dealership where the charge port door fell off enroute to the dealership. At least that is what we can determine. The car was set on the tow truck with the rear of the car facing towards the front of the truck. We believe the wind hitting the car from a direction that would never happen during normal driving caused the door to go flying. If anyone has any better ideas on what happened I would love to hear them. So this little adventure cost me $275 for towing the car 45 miles, $400 dollars for a replacement door(Includes labor and painting),the actual door was only 22 dollars, and the dealer only charged me $199 for troubleshooting and did not charge for anything else. My main concern is no one knows what happened, including GM as they told the dealership that they have never seen this before. So should I be concerned? I have spent right around $900 dollars and no guarantee it will not happen again. Has anyone else seen anything like this? Thanks!