On my 2004 Chevy Silverado, the "service 4 wheel drive" message has come on twice. The first time the 4wd worked fine, but the dash light showed the transfer case in neutral while driving down the road. I checked all fluids and electrical connections all were fine, and the message went away. A couple months later the message appeared again, this time the 4wd would not work,
transfer case would not switch to 4wd. After a couple attempts, backing up and shutting the truck off and restarting it worked.( I really needed the 4wd)
The message has not appeared again. Any ideas?