Circuit/System Description
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2008 GMC Yukon XL, 2008 GMC Yukon, 2008 Chevrolet Tahoe, 2008 Chevrolet Suburban, and 2008 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
When the turn signal/multifunction switch is placed in the headlamps high or flash to pass (FTP) position, ground is applied to the body control module (BCM) through the headlamp high beam signal circuit or the flash to pass signal circuit. The BCM applies ground to the headlamp HIGH BEAM relay control circuit which energizes the HIGH BEAM relay. With the HIGH BEAM relay energized, the switch contacts close allowing B+ to flow through the HI BEAM fuses to the high beam headlamps. Ground for the left headlamp is supplied at G100 and the right headlamp receives ground at G101.