Circuit/System Description

The accessory dc power control module (APM) converts the energy that flows between the high voltage, 300 volt, direct current (DC) to intermediate voltage, 42 volt, DC to support the electric power steering (EPS). The APM receives a 42 volt enable command from the hybrid powertrain control module (HPCM) over the high speed hybrid GMLAN communication circuit.

The APM continuously monitors the status of its 42 volt circuitry. It will do some diagnostics on this circuitry when the ignition key is first turned to RUN. Additional diagnostics are run while the APM is doing 42 volt conversions after receiving the 42 volt enable command.