My 2006 Silverado Z-71 has recently started showing the “service 4wd” warning. I’ve tried all I know to try. I’ve replaced the transfer case control module, the in dash switch, cleaned the ground connections on the frame, checked fuses, & cleaned all connections with electronic cleaner. The electronic shift motor on the transfer case was replaced last spring. I’m at the end of my wits. If anyone has any advice, it would be greatly appreciated.