Circuit/System Description
WARNING: This page is about a different car, the 2009 GMC Sierra and 2009 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The battery energy control module (BECM) performs tests on its own internal memory to detect failures. No external circuits are involved. Failure of these diagnostics can cause erratic hybrid drive motor battery and HV contactor relay operation.