It appears that the location of this switch is different from that noted by an 03 STR owner.

Waiting for dealer replacement of defective latch mechanism but when lid is physically closed, "Trunk Open" is still displayed on dash.

My lid (minus the latch) and lower striker panel on trunk edge are shown below.

 

The little plastic door in the sill, around the latch.

 

No, nothing in the sill either.

Maybe it's in the latch mechanism? The wiring diagram only shows that there is one, not its location. I guess I'll see if the fault goes away when I get a new working latch delivered and installed.

Thanks anyway.

 

I was mistaken on that. I had a different car in my thoughts. I checked my S Type this morning and it is on the lid. It is a booted switch on the latch.

 

Well, it turns out that the trunk ajar switch is located INSIDE the trunk latch on my model - no booted switch nor rubber buttons anywhere. It took 2 latches from the dealer to solve the problem since the first one was defective.