This is what I have follow it to the T. If not working, it's possible the remote you bought isnt for your truck.
Method 1 - No Tools Required, Program All Transmitters
1. Close all the vehicle doors.
2. Insert the ignition key into the ignition lock cylinder.
3. Press and hold the door unlock switch.
4. While holding the door lock switch in the unlock position, cycle the ignition ON, OFF, ON, OFF.
5. Release the door unlock switch. The doors will lock and unlock to confirm the program mode.
6. Press and hold the LOCK button and the UNLOCK button simultaneously on one transmitter.
After a delay of approximately 15 seconds, the doors will lock and unlock to confirm the
programming of that transmitter.
7. Repeat the previous step to program up to 4 transmitters.
8. Turn the ignition switch to the RUN position in order to exit the keyless entry transmitter
9. Operate the transmitter functions in order to verify correct system operation.
IMPORTANT: All transmitters which are to be recognized by the PDM must be
programmed in a single programming sequence. When using this
program method, all previously programmed transmitters will be erased
upon the receipt of the programming signal from the first transmitter.
The order in which the transmitters are programmed will determine its
numbering position within the PDM memory. The first transmitter
programmed will be transmitter #1, and the second transmitter
programmed will be transmitter #2. The number stamped on the
transmitter case is for reference only; #2 can be programmed as #1, or
vice versa. Additional unnumbered transmitters are also available.
KEYLESS ENTRY SYSTEM -2005 Chevrolet Silverado 1500
Monday, October 31st, 2011 AT 8:26 PM