I would recommend:
1) Swing by a parts store and have them read any codes (if any are present). Record them. Have them 'clear' the codes too. Maybe it was a fluke that won't return. Also have them load-test the battery ...just to be sure. A suspect batt or connections make these trucks act strange (really).
2) Double-check the harness connector (and wires) at the Xfer case. Look very carefully with a strong flashlight for corroded connections or bulging (corroded) wires nearby the connector. Esp being from wintery MI. If someone formerly pierced the wire jacket with a test light, it could corrode the wire at that point. Also look at the fuses in the fuse box.
3) Make sure your battery cable connections are clean and good. If you didn't get the codes cleared (above), Remove both connectors, clean ...and leave them disconnected for 15 min, or so, to clear the truck's codes. See if it returns.
4) If the light goes away for a while, cycle the 4x4 through it's various modes, if you can.
That's about all I can think of. While you're under there, check the fluid level.