Jimmy 98 stuck on 4HI

My 98 Jimmy 4x4 transfercase on 4HI all the time ,even though auto tranfer switch indicates that is on 2Hi. I had this Jimmy lifted up to confirm that front wheels are moving. and when I disconnected the controler fron t.case ,it disengaged the front wheel. What do you think the problem here (shift motor encoder or relay or something else)?

also when I turn the streering will to leflft or in centre I'm hearing this humming sound but not when it's turn right.