Having a problem with my 4wd

[FusionX]

Hi, I just picked up a 99 tahoe with the 4 push button 4wd. The light on the buttons quit working and its not engaging in 4wd. When I push the 4 high it makes a clicking sound and thats it. I had it in auto when i got it and spun on some ice and the "service 4wd" light came on and turned off when i restarted the truck. I found out today that the 4wd didnt work when i got stuck on some ice. What could be wrong with it?

 

[AZRiverRunner]

Probably the controller, cost me $250 for the dealer to replace on my 2003 K2500HD Duramax last year.