does anyone know if tilt sensors are compatible with factory alarm systems or do you have to have a aftermarket security system installed first?

 

You can wire the tilt sensor to the factory alarm. There are 4 wires in the tilt sensor. +12 and ground are self explanatory. Trigger wire should be connected to the trunk trigger wire in the bcm. Last wire is to tell the tilt sensor when the car has been parked.

 

^^modme really knows his stuff.

 

"Last wire is to tell the tilt sensor when the car has been parked"
what does it need to be connected to?