i also have that button on my car which has an alarm .. its used to deactivate the alarm .. like if the alarm was ever going off and your remote did not work youd have to hold down that button as you start the car and the alarm will stop and the car will start ....sometimes when i disconnect the battery and reconnect it my remote will not work so the alarm will be going off and ill have to jump in the car quick hold that button and like i said start the car and the alarm is deactivated ...