how to change the battery in the key fob

That information would be in the owners manual. It is likely the battery and make sure you use the proper battery. Some of these FOBs are very picky when it comes to the battery.

http://www.paulstravelpictures.com/Ford-Explorer-Smart-Key-Fob- Battery-Replacement-Guide/

It requires reprogramming the GEM. really simple, dealer parts, then ask service to get the NGS and go thru the motions. if you have battery condition with dirt or film, they solve it then. if batteries? then, if you have troubles? they order a new set or sell you another set, then back to the top of this paragraph.

If you want to clean yours, then use an eraser.

when you go about it some other way, you spend your time, buy things you dont need of lesser quality, become dissatisfied, still arent sure whats the current issue at that moment, cannot reprogram your GEM yourself. to me, that's just not worth getting fusterfated., and have it still have to get serviced properly.

This is an old thread, but it does NOT require reprogramming the Gem module unless it's programming is corrupt. Replacing FOB batteries every couple of years is a good maintenance plan.