my bad. i read more of the manual, and you are correct. some garage door openers are "rolling code" which are code protected. you can check if you program your homelink by completing the steps above, then press and hold the homelink button. If the red light flashes rapidly, then turns solid after 2 seconds, then your garage door is equipped with "rolling code" technology. you need to do these steps in addition: (note: the following steps are from the 2000 user's manual)
1. locate and press the training button on the garage door motor head unit. if you can't find it, go to HomeLink.jci.com
2. press and release the homelink button. press and release the homelink button a second time to complete the training process. some openers require you to press and release a 3rd time.
It says the second or third press from step 2 should activate the door.