I have a 2010 ford expedition XLT with no Sync or sub, standard factory stereo. I had the HU replaced professionally with a kenwood DDX419. Just noticed the back speakers are not working. I've taken it back and they can't figure it out. I've taken the radio out and checked wiring and also took back speakers out and can't seem to find anything wrong. My question is... Is the rear radio control locking out the speakers? It has the headphone icon on screen but controls do not work. They told me the rear radio would not work with aftermarket HU. I'm ok with that but would like sound back there. Is there another adapter to use? Thanks for help in advance!