2004 GMC Envoy Remote Programming Procedure:
IMPORTANT: Before entering programming mode, have with you all of the fob you want to use on the vehicle, including old ones you want to keep working. Once you program the transmitter, all previous learned remotes will be eliminated from the memory. The other transmitters will not be functional until you program the keyfobs again.
1. Shut all car doors, have windows closed, wait for dome light to go off.
2. Insert the key into the ignition.
3. Hold down the power UNLOCK button on the driver’s door panel-don't let go until step 9.
4. Do steps 5 to 8 very fast.
5. Rotate the ignition switch to the ON position (as far as you can go WITHOUT activating the engine).
6. Move the ignition switch to the OFF position.
7. Flip the ignition switch to the ON position.
8. Turn the ignition switch to the OFF position.
9. Let go of the power unlock button on the door panel. The car will lock and unlock the doors by itself.
10. Hold down the LOCK and UNLOCK buttons on the transmitter together until the door locks cycle. This step may take up to 30 seconds.
11. Repeat step 10 for each and every additional keyfob(including any existing transmitters).
12. Move the ignition switch to the ON position in order to exit the keyfob programming function.