My girlfriend has a 2006 Ford Mustang GT and it was just brought up yesterday that a few years back that her and her dad were driving the car when a loud noise started to sound off in the car. It took some searching but found what looks to be a horn/alarm in the trunk. The car was taken to a couple Ford Dealerships and they didn't know what it was for. They say the car did not come with an alarm so unsure what this is for.

I though it would have be a factory alarm where it would go off if the car was locked with a key fob and unlocked without it like other cars have.

It was disconnected for the longest time then re connected but a little while ago but has not sounded off since.

Anyways anyone have an idea what this might be? It's in the truck on the right side behind the liner.

 

I found info on the "ACTIVE ANTI-THEFT SYSTEM" online and I was able to download the Owners Manual and read up on it.

Service Manual Found HERE http://www.shnack.com/docs/mustang06.ownersmanual.pdf