Tailgate Window Will Not Open From Panel Switch, Otherwise Operates

With ignition switch on, and tailgate open, place panel switch in "DOWN" position. Using a grounded 12-volt test lamp, probe Tan/White wire at panel switch.
If lamp does not light, replace switch. If lamp lights, probe Tan/White wire at window motor, with switch still in "DOWN" position. If lamp does not light now, check for open Tan/White wire between motor and panel switch. If lamp lights, system should operate normally.