Accessory (ACC) Mode
WARNING: This page is about a different car, the 2014 Lincoln MKX and 2014 Ford Edge. However, it is still accessible from the selected car via links, so may be relevant.
When the vehicle enters ACC mode, the message center in the Instrument Panel Cluster (IPC) briefly displays PRESS BRAKE TO START, then displays ACCESSORY POWER ACTIVE. When the vehicle is in ACC mode, electrical accessories such as the audio system and power windows operate upon request.
If the ignition remains in ACC mode for more than 45 minutes, the Body Control Module (BCM) changes the ignition mode to OFF to avoid draining the battery.