Key Fob Stopped Working But Battery Isn’t Dead Join Premium Save. Share Your Car Experience so please excuse my ignorance, but if the key fob thingy was ‘broken’ not the battery would I no longer be able to start the engine with it? Share this post. Link to post Share on other sites Ford Focus Club Key Fob Stopped Working But .Over time, however, the battery will on your key fob, so you’ll need to know how to replace the Ford key fob battery. Afterward, you should not have to reprogram the remote. The project vehicle discussed here is a Ford Explorer, but battery replacement is similar for other Ford key fobs..There are several Ford remotes but in this case, we will show you how to replace the battery on the Ford Smart Proxy Key which is similar to the flip key that uses the same shell. This Ford Key is used on several models with intelligent access such as Ford Mustang, Ford Fusion, F and many other Ford models..Close the plastic cover over the first battery in the bottom of the fob. Install the second CR battery in to the top socket with the ” ” side facing up towards you. Line Up Two Halves Fob Snap Together Key Fob Flush At Every Edge Line up the two halves of the key fob and push them back together..