Replace BMW Key Battery If your BMW key isn't able to open your vehicle or turning the engine, it could be the time to replace your battery. It's a simple fix. It's as easy as removing the key fob, replace the battery and gently put it back. Follow these steps https://carkeyprogramming13337.theisblog.com/30362266/14-common-misconceptions-about-bmw-3-series-key-fob