Circuit/System Description
WARNING: This page is about a different car, the 2013 GMC Yukon XL, 2013 GMC Yukon, 2013 Chevrolet Tahoe, 2013 Chevrolet Suburban, and 2013 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
If the service indicator needs to be turned on the transfer case shift control module sends a signal via LAN to the instrument panel asking the I/P to command the Service 4WD indicator.