My Mark VIII door keyless pad entry doesn't work, I like to go to the park and do a little walking so I like to leave my keys in my trunk, now I can't do that, they will work once I step on the brake or start the car, and they stay working for a little while after I stop the car how long they work you may ask, the shortest time I realize was about 3 to 5 minute, one day I forgot my key in the car, I lock the door via key pad, as I was walking away I remember my keys were still in the car, lucky for me the keyless didn't shut down instantly, that happen to me at work. Have any ideas..