These are the steps you need to follow in order to program fob in Pontiac Montana and Grand.
 No Tools Required. In the event that a key is lost, program the old and the new transmitters into
memory of the remote control door lock receiver. Up to 4 transmitters may be programmed

 OEM Part Number of keys : 15788020 / FCC ID: KOBGT04A and many others ( depending of m.y. ).

  1. Remove the ignition key from the ignition lock cylinder.

  2. Close all of the vehicle doors ( including the Liftgate ).

  3. Remove the MALL PGM / BCM fuse ( Multifunction Alarm Lock and Lighting fuse )

  4. Insert the ignition key into the ignition lock cylinder and turn to the ACC position.

  The Body Control Module will perform the following in order to identify the type of BCM installed 
  in the vehicle: Flash the seat belt indicator 2, 3, or 4 times or Chime 2, 3, or 4 times.

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

  6. Open and then close any vehicle door. 

  You will hear a chime when the remote control door lock 
receiver enters the programming-

  - diagnostic mode. If you do not hear a chime, start again at step 1.

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

  After approximately 7 seconds the BCM will chime once to confirm that synchronization has been   
  completed. After approximately 14 seconds the BCM will chime a second time to confirm that the 
has been completed.

  8. Repeat the previous step in order to program each additional transmitter. 
  9. Remove the ignition key from the ignition lock cylinder.
10. Install the MALL PGM / BCM fuse back into the fuse panel.

* All transmitters which are to be recognized by the remote control door lock transmitter ( RCDLR ) must be programmed in a single programming sequence. If the system is placed in program mode
it will erase all previously programmed transmitters upon the receipt of the programming signal from the first transmitter. Up to four transmitters can be programmed. Do not operate or program
the transmitters in the vicinity of other vehicles that are in the keyless entry program mode.
This prevents the programming of the transmitters to the incorrect vehicle.