I just got a second keyfob and by putting the great advice garnered from several different posts on this forum I was able to program it. The only hard part was the advice was fractured onto several posts. There also was not a clear explanation (that I found anyway) of what to do with more than one fob.
In the interest of putting all the instructions in one place I post them here:
(If you are simply replacing a fob then just follow the first part of the instructions (up to step 6) and you're done.)
I recommend you do this in bright sunlight, or you will need a light up under the dash. The GREEN BUTTON is little.
1. Find the small, black alarm box. It's INSIDE the truck on the firewall, up under the dash a bit. It's the LEFTMOST BOX from the brake pedal. In the center of this box, on the bottom is a TINY GREEN BUTTON.
2. You'll need your key for this, and it's a two handed job so disconnect your keyfob from the ring; even if you are just adding a second fob. It is very likely you will need to reprogram your first fob (this is what I found anyway).
3. Put the key in the ignition and turn it to "ON". VERY IMPORTANT TO DO THIS.
4. Now get the new keyfob in one hand, have the original one on the carpet where you can grab it easily (if you are doing two at once).
5. Scoot up under the dash and depress the TINY GREEN BUTTON with a small screwdriver (what I used) or pen. It doesn't go in very far. Just touch it and push slightly and it's good.
6. While holding the GREEN BUTTON down depress the arm/unarm (top) button on the fob in your other hand until you hear a chirp. Now it's programmed.
When I did this the first fob no longer worked so I had to do the whole thing again a few times. I think the charm finally was doing them both while the ignition key was turned. In other words turning the ignition key starts the programming procedure and you can do more than one while the key is turned. I could be wrong about this but it seemed to be the way it worked. So I recommend you program the original fob (if you were adding a 2nd fob) next while the key is still turned.
7. Doing the 2nd fob. Let up on the GREEN BUTTON, pick up the other fob (your original), push the GREEN BUTTON again then hold the top button on the 2nd fob until it chirps.
Now you should be good to go.
8. Unturn the key and remove it, shut the door and test both fobs. They should both work.
I wonder how many fobs you can add?
Note: If I am wrong about any of this please correct me. The original fob not working, and how I got it working, is the only part I am slightly unclear on. I'm pretty sure it was the keeping the key turned while programming both of them thing though.
Thanks to all the folks on this forum before me who made this a pretty simple job thanks to their instruction.
By the way, Ebay is a great place to get the fobs. I paid $17.00 including shipping.