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 place it back. Follow these steps https://thekeylabcouk82158.bloggazza.com/29522549/then-you-ve-found-your-bmw-3-series-key-fob-now-what