I reporgrammed my remote keyfobs tonight, and ran across the procedure in the owners manual for reprogramming the keys. My manual is a 2006, so your mileage may vary...here is what it said.
Programming spare keys
A maximum of eight keys can be coded to your vehicle. Only SecuriLock keys can be used. To program a coded key yourself, you will need two previously programmed coded keys (keys that already operate your vehicles engine) and the new unprogrammed key(s) readily accessible for timely implementation of each step in the prodcedure.
If two previously programmed coded keys are not available, you must bring your vehicle to your authorized dealer to have the spare coded key(s) programmed.
Please read and understand the entire procedure before you begin.
1. Insert the first previously programmed coded key into the ignition and turn the ignition the 1 (OFF/LOCK) to the 3 (ON) postion [maintain the ignition in 3(ON) for at least three seconds, but no more than ten seconds].
2. Turn ignition from 3 (ON) back to the 1 (OFF/LOCK) position in order to remove the first coded key from the ignition.
3. Within ten seconds of removing the first coded key, insert the second previously programmed coded key into the ignition and turn the ignition from the 1 (OFF/LOCK) to the 3 (ON) position [maintain ignition in 3 (ON) for at least 3 seconds but no more than ten seconds].
4. Turn the ignition from the 3 (ON) back to 1 (OFF/LOCK) position in order to remove the seconded coded key from the ignition.
5. Within 10 seconds of removing the second coded key insert the new unprogrammed key (new key/valet key) into the ignition and turn the ignition from the 1 (OFF/LOCK) to the 3 (ON) position [maintain the ignition in 3 (ON) for at least three seconds, but no more than ten seconds]. This step will program your new key to a coded key.
6. To program additional new unprogrammed key(s) repeat the procedure from step 1.
If unsuccessful, the new coded key(s) will not start your vehicle's engine and the theft indicator will flash on and off and you may repeat Steps 1 through 5. If failure repeats bring your vehicle to your authorized dealer to have the new spare key(s) programmed.
So, from what this says, if you have two working, coded, keys, they you can code more yourself. If you don't, then you need to see the dealer.
Chris