2014 Goes completely dead on shutdown.

I've had this problem... But I'm Gen2 and you're Gen3 so it might be different?

Some kind of loose connection near the 12v battery I think... It always goes away before I take everything apart back there to clean and inspect. My sense of it is that when you turn the car off a relay that shuts the car off for some reason fails to leave the 12v on for stuff that's still powered when the cars off.

What I can tell you is that if you watch your speedometer gauge (aka: combination meter) the last thing to shut off on that screen is the indicator for the gear shifter. When you know the problem is back, those lights don't turn off last, but turn off with all the other ones.

As for fixing it, give a close look at all the connections around the 12 battery. I've never been too thorough because just wiggling that stuff fixes it... Going on 6 months without that problem, but thanks for the reminder, I need to put that on my car to-do list.

 

Check the battery voltage, first at the posts, then the jump point, for starters.

 

Makes sense to check that, but in my experience it's something that goes wrong in the actual circuit path of the shut down sequence when you hit the power off button regardless of the battery being at full or an extremely depleted charge.

 

Sounds to me like a loose/intermittent connection to the battery (there are two connections, of course, at the + terminal and from the − terminal to ground).

After you press the power button and make the car READY, the 12 V power is coming from the DC/DC converter, not from the 12 V battery, and in fact you won't even notice if the connection to the battery flakes out after that, as long as the car's still READY.

When you go to power the car OFF, normally the DC/DC converter shuts off, 12 V power is still supplied by the battery, various computers in the car complete their orderly routines and sleep or shut down, and then it's off.

But if the 12 V battery connection has flaked out, then as soon as you push the power button to turn off, the DC/DC converter turns off and *WHAM* there's no power at all, and the car's computers don't even get to complete their power-off routines.

The funniest thing about that is if the 12 V battery connection then gets restored, the car doesn't wake up in a clean powered-off state, it can wake up in ACC or ON because the computers didn't fully transition to OFF state when the power was lost.

You can read about that in hobbit's write-up here (search for: *WHAM* for the first part of the story, then search for: life).

A girlfriend's car once had an interesting self-resetting battery post clamp. It was so in need of cleaning that it only conducted electricity through a small spot that contacted the battery post. When enough current was drawn through it, the clamp heated up and expanded, that small spot lost contact, and boom (or should I say *WHAM*?) the car lost power. Then the clamp would cool and contract and the power was back.