Power door locks

I have a 1996 Chevrolet Z71 with factory alarm, the keyless door lock buttons work ok but the door lock/unlock buttons do not work on either door. The door lock/unlock buttons dont make any noise at all. Any ideas on how to troubleshoot?

Take a look at the wires to the control switches at either door. Power Lock is lt. blue and Power Unlock is white in either door boot. These wires should be + pulse each time you press the buttons. My guess is that one or both wires have shorted out in the door boots.