The 2003 Monte Carlo SS features a number of the manufacturer's technologies that were made for convenience and safety. Among these are onboard remotes most often programmed to your garage door opener, and which can be programmed from your car with just your garage remote.
From your Monte Carlo, with your garage remote in hand, press and hold the two outer of the buttons on the HomeLink onboard system.
Hold the two buttons until the LED light on the onboard system face starts blinking slowly.
Hold your remote within 3 inches of the onboard system and press and hold the Open button on the remote. Hold the button on the HomeLink system that you would like to program at the same time.
Hold the two buttons until the LED light on the onboard system speeds up its blinking, then release.
Press and hold the "Training" button after releasing the two previous buttons and hold until the LED light turns off. This will end the process and you will be free to use your onboard system to open your garage door.
