Have a 2019 3LT that has completely shut off twice in the past 2-3 weeks while the auto stop was engaged. Vehicle has a new battery (2.5 months old) and I've noticed that the battery voltage immediately plummets when the auto stop engages. On the two instances where the vehicle completely shut down (wife was driving each time), the vehicle shut off with the check engine light displayed. After a short period of time, few minutes on one occasion and right away on the other, the vehicle started right up. We had the vehicle quickly checked at Auto Zone and their tests said the battery, alternator/charging system were operating normally during their test.

Other observations I have is that the battery charge varies during operation, from mid 13's to 14s, but there are occasions where the battery is in the mid 12 volt range while running. Doesn't seem to matter how many accessories are on (AC, radio) as the random variations in the voltage occur whether the accessories are on or not. I've seen comments elsewhere that a battery change might require a software reset by the dealership. I did have the car in to the dealership prior to this behavior occurring where I think they may have disconnected the battery to replace one of the fog light assemblies. However, not sure if this is just one of those random things that can happen with a 6 year old car.

Does this appear to be one of those take in to a mechanic and have them troubleshoot? I live in Hawaii and the repair shops have the customers at a disadvantage in terms of where you can go to get a repair completed. I've experienced some predatory dealerships here with a different vehicle where one slow rolled a warranty repair for so long they now claim its not covered anymore regardless of my copies of the Work Order that shows when the fault was identified and confirmed by the Service Department. I've taken that fight all the way to the automaker's CEO. I know that there are plenty of honest mechanics out there and hope that I can find the right advice.