truck does not go into 4-wheel high

Truck transfer case does not shift into 4-wheel high.Replaced encoder motor assembly did not help.Checked t-case shifted it manually it went into 4-wheel high no problem.Push mode selector button to 4-high encoder motor will shift t-case past 4-high into 2-high.Lights on mode selector switch come on when key is turned on then go off,then no light on to tell what mode you are in.When push any mode button 4-high and 4-low lights come on and stay on.Hope you can help. Truck listed above is a Silverado.