(SOLVED) 2018 F55 Cooper S Dead Stick non-responsive. This has happened twice under similar conditions. The car was parked for a few days. The wife takes it to the store about 5 miles. Parks then presses the start/stop button to kill the engine. That is when it happens, the entire car electronics and engine goes off and will not respond to any input. she calls me to come figure it out. I verify nothing is responding then begin to diagnose. The first thing to do, pop the hood and check the battery. The moment the multimeter probes touch the battery and ground post the car wakes up. Battery voltage was good at about 12.8V. Every thing is working in the key on engine off case at that moment. The only error shown is the time is reset. I started and stopped the car there a couple of times with no problems. The car was driven several time after that with no problems. Then last weekend it happened again. The only difference this time is that when she opened the door it woke up. Same as the first time the only error was the clock reset. I tried searching for similar issues on here but didn't find any.

Does anyone have any ideas or experienced anything similar?

 

(Solved) So it happened again today. As soon as I pull the battery terminal cover the car wakes back up. Wife is ready to drive it back home(she already has groceries in the car). I'm like no let me look at this for a minute. I pushed on the the positive post and it feels funny. I pulled the battery cover and sure enough the positive battery terminal was loose. The mechanic that was in there in January didn't tighten it. It took until September to vibrate it self loose enough to become a problem.

 

Good to hear it ended up being a 'simple' fix. Electrical gremlins can be a real pain sometimes, but an intermittent contact on the battery terminal can cause some real interesting results.