At 219,000 miles, the transfer case motor on my 2002 Ford Ranger XLT was dead (corroded/frozen) and the truck would not go in to 4WD mode.
Thanks to the information posted on this forum and elsewhere, I was able to fix my 4WD problem. First, I confirmed that the problem was NOT caused by a blown fuse or faulty control module, as the 4WD and 4High lights both came on when starting the truck and I could hear a clicking sound after turning the ****. Next, I checked and cleaned all wire connections that were easily accessible. While checking the wires for the transfer case motor, I noticed that the motor looked to be in bad shape (very corroded and the housing seemed a bit distorted). So, I pulled the motor and opened it up for a closer look. Sure enough, it was frozen solid.
Swapping the motor for a new part (Dorman 600-807 purchased at Advance Auto for $100) fixed the problem. The new transfer case motor fit perfectly and it was very easy to replace. My only issue was that the original bracket for the wiring harness, which was not included with the new part, did not fit because the notch did not line up. I took care of that after a few minutes of grinding the old bracket with a Dremmel. Simple job and now I have 4WD again!
Hope this helps someone who has a similar problem.