1999 GMC Envoy Owner's Manual - Page 120

yellowblue 4. Hold down both buttons until you see the red light on the universal transmitter flash rapidly. The rapid flashing indicates that the universal transmitter has been programmed. Release both buttons once the light starts to flash rapidly. If you have trouble programming the universal transmitter, make sure that you have followed the directions exactly as described and that the battery in the hand-held transmitter is not dead. If you still cannot program it, rotate the hand-held transmitter end over end and try again. The universal transmitter may not work with older garage door openers that do not meet current Federal Consumer Safety Standards. If you cannot program the transmitter after repeated attempts, refer to "Training a Garage Door Opener with Rolling Codes" later in this section or contact the manufacturer of the unit at 1-800-355-3515. Be sure to keep the original hand-held transmitter in case you need to erase and reprogram the universal transmitter. Note to Canadian Owners: During programming, the hand-held transmitter may automatically stop transmitting after one or two seconds. In this case, you should press and re-press the button on the hand-held transmitter every two seconds without ever releasing the button on the universal transmitter. Release both buttons when the indicator light on the universal transmitter begins to flash rapidly. Operating the Transmitter Press and hold the appropriate button on the universal transmitter. The indicator light comes on while the signal is being transmitted. If the hand-held transmitter appears to program the universal transmitter but does not open your garage door, and if the garage door opener was manufactured after 1996, the garage door opener may have a "rolling code" system. A rolling code system changes the code of the garage door opener every time you open or close the garage door. To determine if you have this system, press the button on the universal transmitter that you have programmed already. If the indicator light flashes rapidly for one to two seconds, then turns solid, the garage door opener has a rolling code system. In a rolling code system, the garage door motor head unit must be trained to the universal transmitter. 2-60