Mysterious shutdown this weekend

Well, I have new information to share. The dealer originally wanted to return the car to me with another "failure to diagnose" diagnosis, but after convincing them that the numerous codes - all related to losing communications with related braking systems on one side of the car - meant something must be going on, they discovered that the brake ECU had unequal resistance between the two sides. They got authorization to replace the ECU and the wiring to the speed sensors, all under the extended warranty. It'll take a couple more days to get the parts in, and I haven't seen the detailed report yet, but I think they're onto the underlying problem. In my original post, I assumed the car must have been missing codes since none of them related to a hybrid system shutdown, but in both events, the braking system failed first, and generated codes that were stored.

I also didn't mention the other event that happened after the second shutdown. I drove the car to the dealer (just half a mile from our house), and just out of our driveway, at a speed of 18 miles per hour, the VSC cut power to the drivetrain. It stayed on for a few seconds (while I was braking for a stop sign), then turned off long enough for me to make it through the intersection. After about a hundred feet, the VSC turned back on, along with the ABS warning and the circle in parentheses (but no TOD). I pulled over and prepared to restart, but before I came to a full stop, the VSC went off, and I continued driving. I pulled up to the only stoplight between my house and the dealer, and while sitting there, the rest of the lights turned back off - so when I handed it over to the dealer, there was no longer any indication of a fault in the cabin. That was enough to convince me that something in the braking system had to be wrong.

 

Appreciate the input. I figure that since the trouble codes don't point to a component that's obviously failed, I need to keep all the suggestions I haven't investigated open as possibilities. Getting the dealer to replace the components they are currently replacing under warranty is a really good thing, because among the current hypotheses, I'm sure these are the most expensive. The ignition coil would be my next target if the problem continues. I'll keep everyone informed.