Circuit/System Description
WARNING: This page is about a different car, the 2009 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
The engine control module (ECM) monitors the deviation of the voltage across the battery pack, using the 3 module voltage sensors. If one module within the battery pack is not within the expected value, it will manifest itself in a high Delta V SOH (state of health).