Better safe than sorry, so I wanted to find out how to replace the key fob battery before I need to do it. This is for the Denso 14ACX fob. It's easy -- just be gentle and slow. First, remove the metal key. Next to where it stows you'll see an opening in the plastic fob case into which the tip of the metal key fits perfectly. Insert the tip of the metal key and gently twist to pop open the cover. When it pops use the metal tip and glide it along the closed portion of the cover as gently as possible until the cover is completely off. Under the circuit board (lift gently) is a 1632 button cell. Remove and replace the button cell and circuit board and then reassemble the case as gently as possible. Voila!