Replace BMW Key Battery If your BMW key isn't opening the doors of your car or turning on the engine, it could be time to change your battery. Fortunately, it's a simple fix. You simply need to remove the key fob, then replace the battery and gently place it back. https://car-key-reprogramming21236.blogsvirals.com/29649663/the-top-bmw-key-fobs-gurus-do-three-things