After 3 years of searching for the cause of the annoying Service 4 wheel drive switch, I have found the problem!
Pull your VIC out of the car and take apart to expose the solder area of the back connector. My VIC had bad solder joints from the ageing and vibrations. I scratched off the conformal coating on the solder area and re-solder all connections. I put it back together and re-installed in the Jeep. Have not had one error since.
