95 GC "service 4wd switch"

For some reason the cluster can not tell what position your transfer case is in. It's not a critical thing if your transfer case is shifting properly. (i.e. you haven't been in a wreck or bounced off something that could have smacked the transfer case) Like a big rock :D

Shift it through the settings and back to see if that fixes the problem then get under and disconnect/reconnect the plug at the sensor on the transfer case. Should be a oval four conductor up on the transfer case.