Up for sale is a old Gen Saab 9-3 Central locking door hatch lock actuator.  Good functional unit removed from an 02 9-3.  Comes with a 60 day functionality warranty.  This part listed at 1/3 "saab list" price.  Part numbers-  49 47 685  /  655329

If when you un-lock your car with the central locking, and the trunk does not un lock, OR if you un lock your trunk with the key, and the other locks do NOT un lock, most likely this unit is defective.  This is an easy fix.