Crazy electrical cut out issue...

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Anyone come across this little gem on a first gen ('13)?

Just had a cage put in the car so almost everything was stripped but still enough intact that I was able to drive to the shop with no issues. Install went beautifully. Friday I reconnected all the harnesses/modules under the driver side dash at the shop. Car fired right up. Shut car and left for the weekend. This afternoon the shop started the car and backed it out so I could pick it up tonight. No issues. I get there tonight, unlock with the fob, turn the key, car fires right up. All good so far.

It's night time so I have the headlights on, I'm sitting in the car with it idling to warm up while I belt in and suddenly the engine cuts and everything goes dark. Not even brake lights when pressing the pedal. Turn key off/on, nothing. Press alarm fob, nothing. While sitting there, power comes back (headlights come on, I never shut the switch). I turn the key, fires right up like a champ. Doesn't seem like a low battery situation, easy crank. Let it run for a little and about a minute later, it goes dead again. I haven't moved, neither has the car. I don't turn the key off. About a minute later, all power comes back, headlights on, dash lights up. Click the key to the start position, fires right up. After a minute-ish, dies again. I get out, close the door, wait a minute and see the headlights come back on. I click the fob to lock the car and set the alarm. All good. Click the fob to unlock the car. All good. Get in and start the car. All good. Runs a little bit, then all power cut. Minute later, all power comes back.

Is it possible this is something with the immobilizer or does it not act that way? There's no smell of smoke or electrical burning. The fuses all look good. The harness looks good. I didn't have a volt meter to measure the battery voltage but it's only about a year old Shorai. I disconnected and reconnected all cables running to the 2 dash modules next to the steering wheel. Even tried tugging on the connectors while the car was running. Doesn't seem to change the pace of the cut out. Seems way too consistent to be a random short.

It was getting cold and late so I didn't try the 4/13 jumper for the immobilizer reset. Didn't have half an hour to stand around waiting for it and if it was a bad battery thought it might be catastrophic if the battery went during the process. I should note that I only have 1 key for the car so I can't try an alternate fob. I did replace the fob battery last year and the car isn't used all that often.

Before I get the car towed home, does this sound familiar to anyone? Any ideas? Tomorrow I'm going back with a volt meter and the '15 with a known good battery to check that aspect, I'm also going to run a timer to see if the cut and restart is at a definite fixed interval. It seemed that way. Otherwise, I'm stumped.


Edit: Forgot to mention, car doesn't need to be running to have the power cut. Get in, turn key to accessory, wait... power drops. Power comes back. All at about the same interval.

[Ohio Enthusiast]

Check the battery connections (and the master fuses there) and after that, chassis ground points.
I had kinda similar symptoms after a body shop snapped the negative terminal connection bolt and didn't bother to replace it nor tell me about it.