If your keyless entry 'fob' still doesn't work after replacing the battery, it might just be a problem with worn out contacts inside the device.  These contacts are rubber-like, yet coated with an electricity conducting film that can wear off with use.
A typical keyless entry 'clicker' for your car looks like mine. 
By using metallic tape and a hole punch, you can fix it....and the fix works g-r-e-a-t !
Tools needed:
metallic tape or (aluminum foil, for which you'll need a tiny amount of glue to make the dots adhere)
hole punch
a little  bit of manual dexterity

Disassemble the device as shown in the pictures.
Using the hole punch, cut out a "dot" of the metallic tape to place over the worn-out contacts inside the 'fob'.
If you cut the dots from aluminum foil, you might want to use tweezers to put the dots in place. I found through trial and error that super glue does NOT work for very long. I happened to have the roll of what I call 'muffler tape' (that's what it looks like to me and I don't rememnber where I bought it, or for what purpose originally)
I just had to repair mine again today after about 9 to 12 months of service. Beats the price they want at the dealer for a new one.
The pictures should tell the story. Good luck.
    i just re-did both 'fobs' this morning, June 30, '12, by necessity..the tape dots were coming loose again.   This time, to help the metallic tape 'dots' stay in place better I thoroughly cleaned the rubber-vinyl insert to the fob that the tape dots adhere to.  Maybe because it's in Florida, (lot of hot weather) or just general use that allows oils from your hands to enter the deveice over time, the insides of both mine had a distinct 'oily' feel to them.  So I washed them with soap and water, dried them off, then used rubbing alcohol to finish the cleaning.  I also decided to use a pair of tweezers to both separate the paper backing of the tape, and to put the dots in place. In the past I used my fingers to handle the dots and that may have compromised the glue-to surfaces. They seem to more secured now than before.

Drhoades111 month ago
This did not work at all for me
As a matter of fact it made the buttons worse and do nothing at all. I followed instruction completely.

Thank you, thank you!! We just did this with the adhesive backed metallic tape and it worked immediately. Thanks for saving us $78.95 b4 tax.

Robinlynnn2 years ago
I just want to say THANK YOU! This was such a great idea even if I need to do a re-do in a few months and I just couldn't bring myself to go to the dealer to replace them. You have made my day (yes, my life is that dull).
bobcat1947 (author)  Robinlynnn2 years ago
Robinlynn, I'm very glad it was a help to you. :)
iBorg2 years ago
I have the same problem.....
I looked at your repair. First thing I heard in my head was "you idiot." Why didn't I think of that. Definitely going to do this when I get home.

Have you thought of trying either contact cement or nail polish?
bobcat1947 (author)  iBorg2 years ago
Yes to having tried contact cement (worked for a while), NO to having tried nail polish....and I keep a couple of those around for 'ding' repairs; a jar of clear and one black. Great idea you have.. I think that might turn out to be the best "glue" yet. Obviously you'd not want to get any on the surface of the foil that contacts the printed circuit; even if dried, it would prevent electrical current flow. Thanks for the input.
Totally different thought.....
The idea is to create a conductive surface for the button. What about graphite?
I tried this last night. The graphite stuck well to the rubber and seems to work well.

bobcat1947 (author)  iBorg2 years ago
What form did the graphite have? I thought of it only as a lubricant for cable-driven devices such as old school speedometer cables. Where do you buy yours?
Actually what I used was lube for pinewood derby cars
bobcat1947 (author)  iBorg2 years ago
I never knew graphite was conductive; and I can imagine it would cling nicely to the rubber. I've got to try this, when next time a re-do is necessary. Thank you for all your feedback.
Londonbrig02 years ago
what kind of glue would you suggest if using aluminum foil?
bobcat1947 (author)  Londonbrig02 years ago
Hey Londonbrig0 !
No glue has been perfect for this because (I guess) of the vinyl compound of what you're gluing the 'dots' to...seems nothing sticks permanently. The best result has come from super glue, for me. Any of them, - model glue, super glue, vinyl adhesive - has had to be re-done after a few months, maybe in part because of the heat down here. Also, I used the keys A LOT, before I retired. Now they're used far less and are indoors much of the time. Just remember to clean the area of the 'clicker' you're gluing to, before using the glue you choose. Hope this helped :)
MantiZ683 years ago
Works awesome thanks for the idea
bobcat1947 (author)  MantiZ683 years ago
Great ! Glad it helped someone else !