You are _supposed_ to be able to lock and unlock the doors by using the key in the trunk lid.
My car ONLY does this if I do not open and close the doors first. I can cycle the ignition by reaching through the window, adn then the trunk lock will operate the remaining locks on the car. Unfortunately, one would normally turn the ignition off, open the door to get out, close the door, then go to the trunk and do stuff, and lock the car when finished.
Actually, my car locks the doors from the trunk lock, but it only unlocks them from the doors. I cannot unlock the doors from the trunk lock UNLESS I get out of the car when I park it without opening the door.
I can LOCK the car from the trunk lock no matter how I get out of the car, but I can only UNLOCK the car from the trunk lock if I climb out through a window -- on my car, this is not all that difficult because I have a convertible, but it can't be right.
If I climb out the window and lock the doors so that I can unlock them from the trunk lock, then the Ignition Bypass circuit is disabled. It seems that the door has to be opened and closed for the Ignition Bypass circuit to be activated when the doors are locked. Since climbing out a window is not a rational thing to do, then the ignition bypass works fine, but the doors do not unlock from the trunk lock. I can't approach the car with packages and put them in the trunk, then open the doors because they are already unlocked -- I have to unlock the the trunk then unlock the doors, or unlock the doors and the trunk unlocks automatically.
The mechanism in the trunk works right, so I think the central locking module must be hosed up somehow. If the doors remain closed, the trunk will lock and unlock the doors, but if the doors are opened then closed, the truck will lock but not unlock the doors.