Replace BMW Key Battery It might be time to change your battery in the event that your BMW key won't open your car or turn on the engine. It's a simple fix. It's as easy as removing the key fob, then replace the battery, and then gently put it back. https://car-key-replacements31684.bluxeblog.com/62264255/what-bmw-key-fobs-experts-want-you-to-learn