B2645 07
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.
The DTC will set when the BCM detects voltage is above 4.9 volts in the ambient light sensor signal circuit or if the ambient light sensor ground circuit is open.