97 K2500, 4x4 not working.

[Bryce]

Just picked this truck up over the weekend. 97 K2500 Silverado 7.4 gas.
I am hoping someone can help me.
It has the push button on the dash 4 wheel system. The whole system seems inoperative. Not even the indicator light for 2 wheel drive comes on.

I have checked the transfer case fuse and the four wheel drive fuse both are good. I can not even find a wiring diagram for this system in a Chiltons manual.

Any suggestions would be helpful. Actuator on the axle??? Transfer case??? Switch panel???

Thanks for any ideas.