2003 GMC Envoy Remote Programming Procedure:
IMPORTANT: Before initiating remote programming mode, have in-hand every keyfob you want to use on the vehicle, including old ones you want to keep working. At the time you program the fob, all previous learned fobs will be cleared from the memory. The other remotes will not be functional until you program the remotes again.
1. Close all vehicle doors, all windows closed, wait for dome light to turn off.
2. Put key in ignition.
3. Press and Hold the power UNLOCK button on the driver’s door panel-don't let go until step 9.
4. Perform steps 5-8 quickly.
5. Rotate the ignition switch to the ON position (as far as you can go WITHOUT starting the engine).
6. Rotate 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 simultaneously 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 fobs).
12. Turn the ignition switch to the ON position in order to exit the transmitter learning mode.