Replace BMW Key Battery It could be the time to change your battery if your BMW key won't allow you to open your car or turn the engine. Fortunately, it's an easy fix. You simply need to remove the key fob, then replace the battery and gently place it back. https://carkeyreprogramming75424.azzablog.com/30285342/20-tips-to-help-you-be-more-efficient-with-bmw-3-series-key-fob