Tools: Small Phillips head screwdriver like for glasses needle nose pliers Battery CR2032 Home Depot or Lowes Spray lubricant ( I like CSP for all car related Found at Home Depot)PO Been a few years and forgot how to take it apart so I searched and never found one with pictures so here we go. Stick it in your documents because sooner or later you will need it.: First remove the hidden metal key. Push the sliding little button on the top of the fob to one side and hold it. While holding it pull the key out. Here's the hard part if you have not replaced the battery in a long time the sliding cover with the silver insignia is pretty stuck on. I remember when the FOB was new you could just just push it off with your thumb. I had to lift one of the end flat cover corners and grab it with a needle nose pliers...while holding it with the pliers slide that same little lock all the way to the side and hold it there while pulling the cover off. See my pictures so you can see which way the cover slides on and off. Its on grooved side rails. Then you can see the battery cover. Using a very small Phillips like you would use on eye glasses unscrew the four screws. Notice there's a relief slot on one side of that cover you can use a knife to pop the cover off. Now notice there's a tiny little rubber O ring around that battery to seal it from moisture. It falls right out. Don't loose it. Remove battery carefully notice the top edge along one edge of the battery. Thats for one polarity of that battery. Don't bust that out. Try knocking the battery out gently by tapping it on a table but you may have to pry it out. Gently. You can continue to take it apart and remove the circuit board and the tactile rubber button assy. If so just remove that board and then with dish washing liquid and a toothbrush scrub the whole plastic assy and then rinse and let air dry. Put that circuit board assy back together and before you insert the battery spray some lubricant in there on the contacts. I did that 10 years ago when it was new and the contacts still look new 10 years later. Also it may save the FOB itself if the battery ever starts leaking. Put the O ring back on and then the little square battery cover and the 4 screws. To get the insignia cover on you have to hold that slide again then install slide cover and release. Before you slide that cover on push one of the buttons and see if the little red LED on the cover lights if it does good job! If it does not check you have the battery in correctly.