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 accessory power module (APM) supplies the energy that flows between the high voltage (300V) direct current (DC) and low voltage (14V) DC to charge the 12V 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.