Mine has this problem too. What I did is to have it lifted and check if the front wheels were spinning in the 2w mode with the Part Time light on. Guess what? it was NOT in 4WD mode at all. I have read somewhere that the sensors of the transfer case go bad and thatīs why you get the "part time" even though the vehicle isn't in that mode. For me is just a matter of replacing the sensor, but in the meantime I ignore the indication, which sometimes goes away. This is a common problem according to what I have read, so you might be having the same issue. Hope this helps.