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 simple to fix. Simply remove the key fob, then replace the battery, and then gently put it back. Follow these steps https://carkeyrepair02630.blogsumer.com/29674416/a-step-by-step-guide-to-bmw-3-series-key-fob