Circuit/System Description
WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The 4 low 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, 4 High and 4 Low LEDs. When the 4 Low mode has been selected, the transfer case shift control module (TCCM) provides a ground through the 4 low indicator control circuit illuminating the LED. At key ON, the TCCM will illuminate and test each mode indicator for 2 seconds.