Circuit/System Description
WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The body control module (BCM) monitors the window lockout command from the driver door switch (DDS). When the rear window switch operation is authorized, the the BCM signal voltage drops approximately 5 volts to the rear window switches allowing for normal window operation from the rear switches. If the rear window lockout function is commanded, the BCM signal voltage is at B+ voltage which disables the rear window switches and the rear windows will only operate when the BCM receives a command from the driver master control.