The fob will need to be replaced then. Check that your programming it correctly.
November, 29, 2011 AT 11:28 PM
You cannot program just one transmitter. All transmitters have to be programmed simultaneously.
Transmitter Programming Procedure (Method 1 - No Tools Required)
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 four transmitters.
8. Turn the ignition switch to the RUN position in order to exit the keyless entry transmitter mode.
9. Operate the transmitter functions in order to verify correct system operation.
November, 30, 2011 AT 7:40 PM
2001 silverado dead key fob follow up. Followed the step by step reprogram you sent. Bad keyfob worked! Good one stopped working. Tried reprogram again, each time, alternate fob dead, freshly programmed ok. Still only one operational.