How is your M2-ATX wired to your car's electrical system? Do you have the +12vdc lines reversed? If you're using MODE 1, it should be shutting down fine. I use Hibernate in windows, but the M2 sends the hibernation signal 5 seconds after I turn the car off, and then shuts down completely after 45 seconds. If the power lines are reversed it would (I think) turn on just fine, but the power off would be a hard off as you would be cutting the power immediately.