Replace BMW Key Battery It might be time to replace your battery in the event that your BMW key isn't able to open your car or turn on the engine. Fortunately, it's a simple fix. Simply remove the key fob, then replace the battery, and then gently put it back. https://the-key-lab61089.diowebhost.com/85290649/an-easy-to-follow-guide-to-bmw-3-series-key-fob