Keep Alive Power (KAPWR)
WARNING: This page is about a different car, the 2013 Ford F-550 Super Duty, 2013 Ford F-450 Super Duty, 2013 Ford F-350 Super Duty, and 2013 Ford F-250 Super Duty. However, it is still accessible from the selected car via links, so may be relevant.
The KAPWR circuit supplies a constant battery voltage (B+) input to the PCM to maintain memory contents when the ignition is in the OFF position.