[BehindBars]

I think the main issue is GM tried to automate start up and shut down to make life easier for the owner. The problem with that is it built around an expected owner/driver behavior, and deviation from that behavior makes the automation work against you.

I doubt there is anything random about your experiences. You’ll need to fully understand the logic in the car and then create a protocol that allows you to leave the fob in the car, if that’s what you want. Personally I would just take the fob with me and everything should work right. We park in enclosed, locked garages but keys and fobs are never left in any vehicle.

Computer inputs that affect power on-off logic are the driver seat belt, driver door open/close, whether the car has seen a drive or reverse and park cycle, and the brake pedal. If your shutdown symptoms appear different sometimes, consider which of those inputs may have been activated differently.

An example might be like if you got in car and closed door. Car turned on. You opened door but car doesn’t shut down because no drive cycle occurred. You turn off car manually with door open. You get out with fob still in car. Close door snd car will turn on because it thinks you just got in car with fob in your possession. You come back a minute later and discover the car is already on.

Another gotcha is accidentally touching the brake pedal on the way out causes an off car to turn back on.