[denverpete]

The most common cause is the center console lid is not fully closed. This can sometimes happen when you lock it with the key and the action also depresses the button.

It is not necessary to have the AC or radio off. However, if you have an aftermarket stereo or a removeable faceplate, this will sometimes cause the vehicle to beep.

Another possibility is hitting the remote button twice in succession. This turns off the interior alarm and gives a beep to let you know.