Stereo & Electronics - Factory security system is crazy need help

I don't know a whole lot about the factory security system so I am needing some expertise. When I set the alarm, the horn beeps normally but about 15 seconds later the alarm will start going off. I then can hit the door lock button again and it will go off and be fine and works the way it should. Why would the alarm be going off after I set it? Could I have a bad knock sensor or something and what checks can I do on the system?Thanks for the help

Very well could be the shock sensor - try disconnecting it temporarily and see if it stops.

yep it was the knock sensor. Unplugged it and it works great Thanx