I just bought a keyless entry and now I need to program it. HOw did I do that?

Keep the windows open as a safety measure, then,

Remove the ignition key from the ignition lock cylinder.

Remove the BCM PRGRM fuse from the fuse panel. Refer to Fuse Block in Wiring Systems.

Close all of the doors.

Close the liftgate.

Turn the ignition lock cylinder to ACC.

Turn the ignition lock cylinder to OFF, and then back to ACC within 1 second.

Open and close any vehicle door. A chime will be heard when the system enters the BCM programming/diagnostic mode.

Important
After 7 seconds, a chime may be heard confirming successful synchronization. It is necessary to wait approximately 14 seconds for a second chime that will confirm successful programming.


Press and hold the transmitter LOCK and UNLOCK buttons simultaneously for 14 seconds.

Repeat the previous step on each additional transmitter to be programmed.

Remove the ignition key from the ignition lock cylinder.

Install the BCM PRGRM fuse back into the fuse panel. Refer to Fuse Block in Wiring Systems.

Transmitter Programming:

1)With the driver door closed, hold down the power unlock button on the door panel.
2)Turn the ignition switch to the ON position
3)Turn the ignition switch to the OFF position
4)Turn the ignition switch to the ON position
5)Turn the ignition switch to the OFF position
6)Release the power unlock button on the door panel.
The remote control door lock reciever will respond in the following manner in order to indicate that the receiver is in the programming mode:

6.1)Locking the doors
6.2)Unlocking the doors

IMPORTANT:
All extra transmitters must be programmed at this time. When a new transmitter is programmed it will deactivate the old transmitters.

7)Hold down the lock and unlock buttons on the transmitter until the remote control door lock reciever will respond in the following manner:

7.1)Locking the doors
7.2)Unlocking the doors
Repeat step 7 for each additional transmitter
9) Turn the ignition switch to the ON position in order to exit the transmitter programming mode.

There... your little GM secret is finally known... Now can someone out there start posting these program codes for the rest of us! Hope this helps....

This is why it don't work. This is one you need a scan tool for. Stupid Idea. The procedures are different for each car, and model year, the one mitch supplied looks like the one for older silverado trucks, not sure though.


Transmitter Programming
A remote door lock receiver may have up to 4 different transmitters programmed. You may program a transmitter to more than 1 vehicle providing the remote keyless entry systems are similar. When reprogramming 1 transmitter, reprogram any and all other transmitters (maximum of 4 total per receiver) at the same time in order for the other transmitters to work.


Important
Leave a window down in the vehicle while reprogramming the remote control door lock receiver system. This procedure will avoid an unintentional lock out if the reprogramming is not performed properly.


Turn off the ignition.
Utilize a Tech 2 to program the remote door lock receiver.
Enter diagnostics (F0).
Enter body (F1); select the year (X) and body style (N).
Select "Remote Function Actuation" (F3).
Select "Special Functions" (F2).
Select "Program Transmitters" (F0).
Select the number of transmitters to program (1-4)
Follow the on-screen instructions; press continue, wait for the locks to cycle, hold the lock and unlock buttons simultaneously for 15-30 seconds, the locks will cycle again.
Exit the vehicle. Attempt to lock/unlock the doors to verify the programming.
Perform the following steps if the above procedure does not program the transmitter.
Reconnect the Tech 2.
Enter service programming (F1).
Press the "REQUEST INFO" key.
Select "Reprogram Existing Module"
Exit the vehicle and remove the Tech 2.
Follow the existing procedure to reflash the body control module.

There are so many different models on teh market that is hard to say. Do a google search on the manufacturer and search that site for user manuals that you may be able to download.