I replaced all 4 of my wheel speed sensor with no luck with the 4WD light. I then read a ton of threads and found it was more then likely the wire harness for the solenoid on the inside of the front or rear diff.
-Hop under your jeep to the rear or front diff.
-At the top there is one wire connection and only one disconnect it.
-Throw some test leads on the sensors 2 male pins and make sure your reading 14 ohms.
-If you read 0 then your wire harness on the inside of the diff to the solenoid actuator is busted.
My front diff solenoid read 0 ohms. Cracked the front diff cover and found the wire harness was completely broke. Replaced the harness $10 part from stealership, replace fluid with mobile1 75-140 with friction modifier from dealership and Service 4WD light went off instantly
. Hope this helps The pic is the harness that sticks out the top of the diff. You can see the two wires that go into the inside of the diff an connect to the solenoid are completely cut off.