Replace BMW Key Battery If your BMW key isn't opening the doors of your car or turning on the engine, it may be the time to replace your battery. It's a simple fix. It's as easy as removing the key fob, replace the battery, and then gently put it back. https://car-key-programming57254.webbuzzfeed.com/30689786/bmw-key-fobs-tips-from-the-top-in-the-industry