GMC Sierra Denali Owner's Manual page 118

8. Return to the vehicle. Firmly press and hold the
programmed HomeLink@ button for two seconds,
then release. Repeat the press/hold/release
sequence a second time, and depending on the
brand of the garage door opener (or other rolling
code device), repeat this sequence a third time
to complete the programming.
HomeLink@ should now activate your rolling code
equipped device.
To program the remaining two HomeLink@ buttons,
begin with Step 2 of "Programming HomeLink@." Do not
repeat Step 1.
Gate Operator and Canadian
Programming
Canadian radio-frequency laws require transmitter
signals to "time out" or quit after several seconds of
transmission. This may not be long enough for
HomeLink@ to pick up the signal during programming.
Similarly, some U.S. gate operators are manufactured to
"time out" in the same manner.
If you live in Canada, or you are having difficulty
programming a gate operator by using the
"Programming HomeLinkm' procedures (regardless of
where you live), replace Step 3 under "Programming
HomeLink@' with the following:
Continue to press and hold the HomeLink@ button while
you press and release every two seconds (cycle)
your hand-held transmitter until the frequency signal has
been successfully accepted by HomeLink@. The
indicator light will flash slowly at first and then rapidly.
Proceed with Step 4 under "Programming HomeLink@'
to complete.
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