Replace BMW Key Battery It might be the 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. Simply remove the key fob, then replace the battery, and then gently put it back. Follow these steps https://www-thekeylab-co-uk70740.blazingblog.com/30287317/5-bmw-key-fobs-projects-for-any-budget