Replace BMW Key Battery If your BMW key isn't opening the doors of your car or turning over the engine, it could be time to replace your battery. It's a simple fix. You simply need to remove the key fob, then replace the battery, and then gently put it back. https://carkeyreprogramming55723.full-design.com/the-advanced-guide-to-bmw-3-series-key-fob-72798269