Replace BMW Key Battery If your BMW key isn't opening the doors of your car or turning over the engine, it could be the time to replace your battery. It's a simple fix. You simply need to remove the key fob, then replace the battery and gently place it back. https://thekeylab81881.izrablog.com/30703383/15-reasons-why-you-shouldn-t-be-ignoring-bmw-3-series-key-fob