I've seen the Service 4wd message come up occasionally. The truck won't go into 4wd while the message is displaying. The truck goes into 4wd fine afterwards. I've read a little an am encouraged that often the light shows up often from lack of use. I'm now engaging the 4wd more often just in case it's a lack of use issue. I just purchased the truck and first saw the message 3 days ago. I'm planning on 4wheeling on the hatteras beach in a month.