Relay Controlled Power Mode
WARNING: This page is about a different car, the 2011 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.
The body control module (BCM) uses the discrete ignition switch inputs Run/Crank Ignition 1 Voltage, Accessory Voltage, and Ignition 1 Voltage, to distinguish the correct power mode. The BCM, after determining the desired power mode, will activate the appropriate relays for that power mode.
The RAP relay remains on for a timed period after the Ignition key is removed. Refer to Retained Accessory Power Description and Operation for more information on the retained accessory power (RAP) function.