my 99 gmc sierra switches show switched to 4 hi but wheels do not engage, on 1999 GMC Sierra 1500

no trouble codes have come up did put a new stereo system in truck and had to remove battery positive for about an hour could this have caused it. not sure were to locate the fuses for the 4x4 system if there is any

Asked by for the 1999 GMC Sierra 1500
sounds like encoder motor do you hear any clicking when changing into 4wd?if not I would suspect that or possible reflash computer at dealer