2002 Mustang GT factory alarm keeps going off

It sounds as if the car believes the door is ajar. I know on my car it gets fussy when I gentally close the car door and it honks at me twice. Now with the alarm randomly going off.. I believe someone else on the forum had that issu and it turned out to be his door ajar switch or something like that which will be difficult to hunt down from what he was saying. Good luck though. There are several people here that are very knowledgeable about the ford pats system though so you will find out the issue in no time.

Mine was doing the same thing one day. Turned out one of the map lights on the rearview mirror had been left on.

The above suggestion is probably in the right direction. Make sure the door switches are working properly, no interior lights or trunk light are on.

I don't see any lights on in the car at night. I've tried closing the doors, hood and trunk multiple times and the problem persisted. If a door was open, wouldn't the map lights be on?

I had this issue on my 96 mustang. I never could track down what was causing it.

What I had to do was use the lock button on the door to lock the car before turning the car off. When I did this the doors would be locked and the alarm wouldn't go off. If I used the key FOB it would go off every time. If I remember correctly if I locked the doors after car was off with the door button it would cause alarm to go off as well... I know this isn't a fix, but rather a way to lock your car without alarm going off until you are able to track down the cause and are able to fix it.

Too your question the map lights should be on when the door sensor is saying door is open. All it takes to set the alarm off though is a flicker of a sensor saying a door, trunk, or the hood is open and it will go off.

Good luck.