that wire goes from a control module, to the dome light... it is grounded when a door is open, and if you ground it, it will turn the dome light on. Same wire for both connections.

Why do you want to change shock sensors? It sounds like the new one you have is a single stage sensor, and the one already there is a dual stage. If you want to change them, figure out which wire is which before you go connecting anything together. I suggest you stick with the sensor thats there.