Replace BMW Key Battery It's probably time to change your battery if your BMW key won't allow you to open your car or turn the engine. It's a simple fix. You simply need to remove the key fob, then replace the battery and gently put it back. Follow these steps https://www-thekeylab-co-uk08002.snack-blog.com/30157501/20-things-you-need-to-know-about-bmw-3-series-key-fob