Has anyone had there service 4wd light come on and 4wd not work on there trucks? Mine has the manual transfer case and i cant get the 4wd to engage. It makes a grinding sound when i go to do this. Haven't had a chance to take it to the dealer yet (not that i want to deal with the dealer) and wanted to see if its something i can fix my self. Truck drives fine ect just no 4wd. Could it just be a sensor or something?