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 hybrid powertrain control module (HPCM) continuously monitors the system voltage on the Ignition voltage circuits. The HPCM is located within the drive motor generator power inverter module (PIM) assembly and is not serviced separately. Lower than normal voltage may be inadequate to operate the control module or sensors properly.