Just purchased an 04 envoy with 150k that had the service 4wd light on and 4wd not working. Checked all wires going to and from tccm and everything checked out. Checked for power at encoder motor and that checked out as well. Replaced tccm and that changed nothing. Replaced encoder motor and now there is no longer a service 4wd light on in dash however motor is not engaging. Replaced the 4wd selector switch on dash and that didn't do it either. Fuse in rear panel #48 is good. Pull it out and 4wd light comes on. Put it in and goes right back off. Pull wires from from actuator again service light comes on. Everything seems to be commuting properly but still no engaging on the encoder motor. Any ideas on where to go from here?