I have a 2007 Ford Explorer with a stock HU would still turn on but play no sound from the speakers.
So I replaced the front 6x8 speakers and installed a new HU. With the help of the wiring harness and antenna adapter, matching colors and soldering the connections was a breeze. But there was another plug that wasn't being utilized. Attached is a picture for reference.
Powered on the unit and it turns on fine but still no sound.
I checked the wires on the harness that were not used, and they are "amp turn on" and "amp ground" and "illumination", and "dimmer." I assume the amp turn on and ground are for an upgrade separate amp. Right now I just want to get the Head unit working with the stock speakers. Then I will probably upgrade from there, depending on how it sounds.