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.
The body control module (BCM) has 2 circuits for monitoring vehicle system voltage. The BCM B+ is supplied to terminal 3 X3 by the BCM fuse, and the high resolution B+ is supplied to the BCM terminal 10 X4 by the IPC fuse. The BCM monitors the system voltage on both circuits to ensure that the voltage stays within the proper range. Damage to components, and incorrect data may occur when the voltage is out of range. If the BCM detects the system voltage on the high resolution B+ circuit is outside the normal range, DTC B1517 will set.