Who to know which sensor is faulty in alarm system?

[ppbon]

.... the doors
the front trunk
the rear trunk
the oddsment compartment and
the glove compartment (if pertinent).
Most people overlook the oddsment compartment.
Using a PST-II or a PIWIS you can manually activate each one.
But if you don't have access to the System Testers you can get in the car and close the doors.
If the interior lights go out after a few seconds the door microswitches are fine.
To test the trunks, open the lid.
Manually close the latch with a screwdriver and see if the trunk light goes out.
You can do the same with the glove box if you have one.
The only compartment without a light is the oddsment.
Happy Boxstering,
Pedro