A kind person replied to my post with an answer. I'm posting their answer here to help others.
--CaptWiggum
Marcella Wegiel Fri, Sep 16, 2005 at 1:37 PM To: snipped-for-privacy@gmail.com
Thanks for replying. After emailing you I continued to search and found the answer. This is what happens when the alarm has been triggered. The computer isn't smart enough to realize if the key was used or not. Trigger the alarm, and the truck will make sure you know about it for the next few days. If it ever happens again, lock the doors with the key fob as usual. Unlock the door using the key and open it, triggering the alarm again. Turn it off by pushing the unlock button on the key fob. This should reset the computer. Or you can just a wait a few days for the alert to time out. Thanks!
-Matt
snipped-for-privacy@gmail.com Apr 6, 7:29 am show options >
> I've had a 2005 Chevy Colorado Z71 Crew Cab for about six months now. I
> am very satisfied with it. I have a couple questions that I'd like to
> ask of other owners.
>
>
> 1) When I unlock it using the key fob the horn beeps three times. This
> started recently, I think after my wife accidentally set off the alarm.
> What does it mean and how do I fix it?
>
>
> 2) I hear rattling when I traverse rough road that sounds like hardware
> under the bed. Is there something I should tighten down after 5k miles? >
>
> Any advice appreciated.
>