An electrified powertrain system for a vehicle includes an electric machine coupled to a driveline. An inverter controller communicates directly with an auxiliary power module. An ignition module indicates either a key-on state or a key-off state. When the ignition module is in a key-off state, a low-power DC/DC converter generates an output voltage originating on the high-voltage DC bus having a magnitude sufficient to activate the inverter controller. The inverter controller detects a key-off uncontrolled generator (UCG) mode. The inverter controller directly communicates detection of the key-off UCG mode to the auxiliary power module. The inverter controller controls the inverter. The auxiliary power module supplies electric power to operate low-voltage electrically-powered powertrain actuators.