Replace BMW Key Battery If your BMW key isn't able to open your car or turning on the engine, it might be the time to replace your battery. Fortunately, it's an easy fix. It's as easy as removing the key fob, then replace the battery and gently put it back. https://car-key-reprogramming06530.blogars.com/29407320/5-killer-quora-answers-to-bmw-3-series-key-fob