Driver Power Window Operation (RPO A31 W/O AN3, DL3)
WARNING: This page is about a different car, the 2010 GMC Sierra, 2010 GMC Cab & Chassis Sierra, 2010 Chevrolet Silverado, and 2010 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The switch for the driver power window has 3 positions UP, Down and Express Down and it's position is a direct input into the driver window switch. Upon receiving a request for power window operation (switch activation), the driver window switch supplies voltage to the power window motor left front up or down circuit and grounds the opposite and the power window motor runs to move the window up or down.