2000 GMC truck service 4wd light on, stuck in four wheel drive. on 2000 GMC Sierra 1500

Had truck scaned will not engage code came up ( not sure on code number think it was 323 or 363 not sure). Replaced encoder motor,4wd control module,tranfer case, dash switch, tested wiring harrness,actuator motor,all in working order. What have I over looked?

Asked by for the 2000 GMC Sierra 1500
my guess is the acuator which is a very common failure. there is a updated one available from gm.