Circuit/System Description
WARNING: This page is about a different car, the 2009 GMC Yukon, 2009 Chevrolet Tahoe, 2009 Chevrolet Suburban, and 2009 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
The 4 high indicator circuit consists of a light emitting diode (LED), a LED feed circuit and a LED control circuit. The indicator dimming control circuit is the LED feed circuit and continuously supplies voltage to the 2 High, Auto 4WD, 4 Low and 4 High LEDs. When the 4 High mode has been selected, the transfer case shift control module (TCCM) provides a ground through the 4 high indicator control circuit illuminating the LED. At key ON, the TCCM will illuminate and test each mode indicator for 2 seconds.