Ok, I'm nominally a car guy, but this is our first Mazda. My daughter has a 2013 6 with the 4-cyl engine and automatic transmission that we've had since 2016, but this is the first real unsolvable problem I've encountered with it.

Symptoms: after a tire blowout, car wouldn't start (PROBABLY no connection between those). Got towed to NTB and was told battery was bad. Got new battery, TWO shops told us alternator was fine. The new battery does not stay charged, and the car will start when jumped but now sometimes dies while in motion and requires jumping to restart.

The real oddity is that when you rev the engine a little (in neutral or while driving), it ALMOST seems like the ECU resets because you get the two-tone startup chime and the HELLO message on the console. Also, blind-spot warning on mirror illuminates.

A voltmeter across the battery terminals while at idle shows 14v flowing to the battery, at least at THAT time. I personally suspect a bad voltage regulator that only intermittently fails, but I believe that is internal to the alternator so when several places tell me the alternator is working fine, I'm at a loss.

Anyone have any other ideas, or diagnostics to try? The engine is NOT throwing a code, the tire pressure light is on because it's cold and the tires are low, and the TC OFF light is on I think as a result of the tire light. No other lights are on, and I'm not aware of any built-in diagnostics I can run.

Thanks for any help you can think of.