I recently bought a 2000 Chevy S-10 pickup truck that has the dahsboard partly disassembled. There are two lights under the dash that are always on. I don't see a switch on the door that reacts when you open and close the door. I'm accustomed to older vehicles with a little button that pops out when you open the door. I see no such button on this vehicle. Where is the device that detects that the door is open or closed?