Circuit/System Description: P0AF8
WARNING: This page is about a different car, the 2008 Chevrolet Malibu. However, it is still accessible from the selected car via links, so may be relevant.
The engine control module (ECM) monitors the correlation of the battery energy control module (BECM) battery voltage and the starter generator control module (SGCM) output voltage to detect a 36 volt cable open or fuse/relay failure.