key not working

There is a battery in the "key" that does eventually go dead. The process for replacing the battery is in the car's manual.

Sometimes if your key is in the same pocket with your cell phone the phone interferes with the key. Try moving the key away from your phone and see if that helps.

If the battery actually dies you'll have to use the mechanical key which is in one side of the fob to open the door. The key (fob) will work with a dead battery if you put it in the slot in the dash.

 

Does the other fob still work? If yes then it's probably a bad battery in the first fob.

 

You will need a jewelers screwdriver set and a new battery.
Go to a store and purchase one or two 2032 button cells.
Remove key from FOB.
Press the key removal lever again and slide the FOB apart.
You will see four tiny screws holding a cover. Remove them carefully.
You may need to carefully pry the cover off.
Replace the battery, and reassemble the FOB in reverse order.

If you go to a Radio Shack or many other stores that sell electronics, and buy the battery there, they will often replace it for you if you don't have the appropriate screwdrivers.

 

Only problem is that Radio Shack usually sells CR2032 for obscene ripoff prices, on the order of $5 or more. Places like Fry's Electronics (which the OP may not have near him) sell them for <$2.

One hint of a low key fob battery is that after you've driven for 20+ minutes (?), when you power off the car, the car will beep at you.

 

What a timely topic! I've had the car beep at me when powering off, and yesterday got a key symbol on the dash when I tried to start up. In general, I've been thinking that the battery is going on my fob, and this topic not only gives me the confirmation, but tells me how to fix it!

How cool is that?