Service 4WD

New to the forum. I been reading about the service 4WD error message in the DIC and determined it was the sensor in the transfer case position sensor which I replaced. I did test the switch in the dash first using a dandy youtube video explaining the ohm reading per the switch selection and all the readings were in ohm range. I was excited to finally not have the error message but after the sensor replacement the error came back almost immediately. Question I have is I think it only can be 2 things. Either I have to replace the whole sensor motor unit or possibly the switch is still no good, maybe I didn't test it right? Anyone have any ideas? Important to note that I have no issues with driving it slipping out of 2WD but occasionally I have trouble getting it into 4WD

I replaced my switch, still get the msg. Removed and looked over the servo that does the work to go from 4 X 2 to 4 x 4 (I don't care what GM called it; it's a servo not a controller) and it looks /works fine. There is a brain box behind the pass. kick pnl that is the brain box for this thing. I can't learn any thing about it except it's cost  (for me) a lot of money. My tranny guy read for drive line codes and it showed no codes stored.
EDIT: I can't find the controller behind my head light switch or behind the passenger kick panel or any where else. Anyone know where it is on a 06 1500  Z71?.