Replace BMW Key Battery It might be time to replace your battery in the event that your BMW key won't open your car or turn on the engine. Fortunately, it's a simple fix. It's as easy as removing the key fob, then replace the battery and gently put it back. https://thekeylab-co-uk62880.bloggip.com/30150880/why-all-the-fuss-over-bmw-key-fobs