Have you read the manual.I received different keys with mine and each has a different function. But mine is a 93 and does not open from inside the passenger compartment .Regardless there were valet keys etc in my original set with instructions in the manual
Good luck
PGP
I have the valet key, you are right it does not open the compartment.
but I want to lock the trunk. If I lock the trunk with the big key, it locks the whole car. that's no good for the valet. If I don't lock the car , than the trunk can be opened with the button on the dashboard.
I heard from somebody that there might be a button somewhere like in the glove compartment to lock the trunk.
I think there is a way to lock the trunk without locking the entire car. Try key in trunk in both directions and maybe more than 1 click in either direction . You could leave the driver side door open, when you lock the trunk and that might lock the trunk independently of the doors.I know mine works in ways that never fail to surpise me. Did you find the manual?
PGP
I found the manual, but no mention of securing the trunk from vallet-parking. I can lock the trunk with the master key, and open the door with the vallet key. the vallet-key does not open the trunk but once the door is open, I can pop-up the trunk with the button on the dashboard
Lock the trunk by turning it the opposite way (to the right and withdraw) with the regular key, and give them the valet key. I have not tried it but both my 89s worked that eay. The owners manual for the 140 (92-94) page 31-33 describes it.