Does anyone know why the programming codes for things such as automatic door locks do not on my 99GMC sierra...the one i found were from a friend who has a 00 GMC any help is greatly appreciated.
Hunter

Try this:

Programming your key fob transmitters:

This is the procedure to program the key fob door lock and panic button transmitters on your 1999+ Silverado & Sierra pickups.

Note: You must program all of your key fob transmitters. Re-programming one will disable the others unless you do this to each.
What to do:

1. Close all doors on the vehicle
2. Insert the ignition key
3. Press and hold the door unlock switch. While holding the switch, cycle the ignition key ON, OFF, ON & OFF
4. Release the door unlock switch. The doors will lock and unlock to confirm the program mode
5. On the first key fob, press and hold the LOCK and UNLOCK buttons at the same time. Hold them for 15 seconds until the doors lock and unlock to confirm the programming of the transmitter
6. Repeat step 5 for each of your transmitters (up to four)
7. Turn the ignition to the RUN position to exit the programming mode
8. Operate each key fob to ensure they were programmed successfully

It came from this thread:

http://67-72chevytrucks.com/vboard/showthread.php?t=180448

I did this to reprogram my new key fobb and it worked the first time (I lost my old key fobb.)

maybe i should have been more specific...(i do appreciate that info though) What i need help with it when you reach 15mph my doors automaticaly lock...but when you stop and put the truck in park they do not unlock...but the codes i have found from friends of mine were from 2000 models, and they do not work in my 99...
(this is Hunter(Gremlinafteru) on a friends name...

My bad, try these (if you haven't done so already.)

My truck also had the procedure/codes in the owner's manual as a supplement.

Here's the instructions for my 04 Avalanche. Don't know if it's the same for an 06 - worth a try nonetheless ey?

Programmable Automatic Door Locks - Programming Steps

All Chevrolet Avalanche models come equipped with Programmable Automatic Door Locks. From the factory your locks are programmed to lock all doors when you shift out of Park, and to unlock all doors when you shift into Park. They are also programmed out of the factory to lock the doors when you exceed approximately 15 MPH if the doors are unlocked (say if you did that manually). This is both a safety and a convenience feature.

You can reprogram the Automatic Door Locks to operate to your liking, or completely disable them. The locks can be programmed with four possible settings.

To program your locks read these instructions all the way through first and then follow them:

Put the key into the ignition but leave it OFF (don't turn the key). This is very important.

Bull the turn signal/multifunction lever towards you (as if you were turning on your high beams) and hold it. Do not release the lever. This is also very important.

While still holding the turn signal lever towards you turn the key to RUN (not START) and then back to OFF (not ACCESSORY) twice. When you return the key to the OFF position for the second time release the turn signal. The door locks should lock and unlock. If this does not happen you need to repeat steps one through three.

You now have 30 seconds to reprogram the door locks. You have four possible options

ALL DOORS LOCK/DRIVER'S DOOR UNLOCKS
On the driver's door press the Lock Button once and then the Unlock Button once.

ALL DOORS LOCK/ALL DOORS UNLOCK
On the driver's door press the Lock Button once and then the Unlock Button twice.

ALL DOORS LOCK/NO DOORS UNLOCK
On the driver's door press the Lock Button once and then the Unlock Button three times.

NO DOORS LOCK/NO DOORS UNLOCK
On the driver's door press the Lock Button twice.

If you want to cancel reprogramming the door locks during this time simply turn the key to RUN (not START) and the doors will lock and unlock again. This indicates the procedure has been cancelled and the original setting has been retained.

If you take longer than thirty seconds the doors will automatically lock and unlock, also indicating the procedure has been cancelled.

You can reprogram the locks as many times as you like

^That came from this thread:

http://67-72chevytrucks.com/vboard/showthread.php?t=210751&highlight=door+lock