A couple of days ago the keyless entry stopped working on my key fob. My wife's worked so at least, it was not a problem with the BCM (that receives the signal).
Battery in the fob was replaced only about 6 months back so that was not a likely cause. It measured 3V with a meter and 2.95V with a 1000 ohm load. Sounds good.
I was in the office and had access to a spectrum analyzer (a fancy radio receiver that is used for finding signal strength over a wide range of frequencies). I set the region of intrest to about 330mhz and pressed the button on the fob. No signal. Opened the fob case and cleaned the contacts on the board just under the buttons. They had gotten fouled. Cleaning was done with a flux remover. For good measure, I also removed the battery and cleaned its contacts on the battery and board. Put it back together and pressed the button. Success - saw a blip on the analyzer. Went outside and tried it on the car. Worked without resetting which surprised me a bit. Normally you hold the lock and unlock buttons down for seven seconds while near the car to reset the fob.
The reset information was molded into the inside back cover of the fob. I seem to remember a slightly different method from the owner's manual. Got to check that later. Meanwhile I'm a happy camper.
Oppie