Pin 9 on the 28 pin radio connector is the amp turn on for a 2016 BRZ... so you would need to connect that to the proper wire for a 2013 frs for the door speakers to work. Based on what I’ve read, the amp turn on in a 13 FRS would be pin 9 on the 10 pin connector.
http://www.ft86club.com/forums/attac...4&d=1340370296