Battery Sulfation Mode
WARNING: This page is about a different car, the 2006 Buick LaCrosse and 2006 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
The BCM will enter this mode when the interpreted generator output voltage is less than 13.2 volts for 45 minutes. Once in this mode the BCM will enter Charge Mode. The BCM will then determine which mode to enter depending on voltage requirements.