1996 Taurus Wagon rear power door lock switch

I have a 1996 Taurus wagon. My rear ( at the hatch ) power door lock switch quit working. Both front door switches unlock & lock all the doors including the rear hatch. I have checked the switch at the rear with a digital volt meter and it seems to be working. There is a diode some where in the circuit per the wiring diagram that I have, for just the rear switch. Not sure if that could be causing my problem but I don't know where it is in the harness so I can check it.

Any help would be awesome. Thank You