Circuit/System Description
WARNING: This page is about a different car, the 2010 GMC Sierra and 2010 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The accessory power module (APM) supplies the energy that flows between the high voltage (300 volt) direct current (DC) and low voltage (14 volt) DC to charge the 12 volt battery and power accessories. The APM receives a wake-up signal on a discrete line from the serial data gateway module (SDGM) when the key is turned to RUN. After a successful engine start, the APM receives an enable command from the hybrid powertrain control module (HPCM) over the high speed hybrid GMLAN communication circuit to begin power conversion.