Flash to Pass
WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.
When the turn signal/multifunction switch is momentarily placed in the flash to pass position, ground is applied to the turn signal/multifunction switch. The turn signal/multifunction switch applies ground to the BCM through the flash to pass switch signal circuit. The BCM responds to the flash to pass request by sending a serial data message to the Lighting Control Module. The Lighting Control Module responds to the serial data message by sending a voltage signal through the left and right high beam control circuits. The left and right headlamp assemblies respond by illuminating their respective high beam LEDs momentarily or until the flash to pass switch is released.