Replace BMW Key Battery If your BMW key isn't opening the doors of your car or turning on the engine, it may be time to replace your battery. It's a simple fix. Simply remove the key fob, then replace the battery, and then gently put it back. Follow these steps https://car-key-programming43520.sharebyblog.com/30056066/the-ultimate-guide-to-bmw-3-series-key-fob