In spite of this being a year old thread, I want to add to this discussion, because I searched high and low and could not find much information (or I should say, Incomplete information) regarding my particular Soul setup.
I have a 2012 Soul +, with UVO (infinity sound w/backup camera). It has a JBL amp with 2 connectors that I had a hard time finding pin out info on. The information I did find, was mostly for the standard head unit, and standard amp.
This all started when my battery failed. After replacing the battery, my head unit had no sound. Everything seemed to work, but no sound whatsoever. I suspected the amp, but had to find the correct pin out diagram to find the amp trigger to ensure it was even getting a signal to turn on.
After finding the amp turning ON, I realized my head unit was bad (Yes, of course I tried resetting it).
I went to Crutchfield and found a Pioneer head unit I liked (AVH-X4800BS), and they told me the Metra Axxess kits to purchase, for installing the new head unit and retain my factory amp, speakers, and wiring. I used the Metra #95-7349B dash kit, to install the Pioneer into the dash(no cutting or mods whatsoever). I used an Axxess HYBL-04 SPIDIF interface, and an ASWC-1 steering wheel interface. The HYBL-04 has a prewired plug to fit into the ASWC-1, so throw away the one that it comes with. You won't need it (you DO need the main ASWC-1 module). The HYBL-04 plugs into the 2 factory connectors that plugged into the back of my fried UVO head unit. You have to splice a few wires from the new head unit to the HYBL04 interface as well, but nothing difficult.
I didn't feel like searching for the E brake wire so I purchased a little brake bypass micro relay for $10, and used that for my brake wire. I followed Drunken Swaggers info regarding the camera pins. He has the correct pin outs, and I did NOT need a 3.3V DC adapter! I got one, but it would not work, and I used straight 12V accessory power to the camera power wire. I could not find any definitive specification on the factory Soul camera other than a stock number. Supposedly the Optima uses a 6V camera. I tried splicing the existing USB cable to a normal USB cable, but the head unit does not want to accept that (because it is part of that Aux/USB module in the dash, that is powered). The HYBL-04 claims to retain the Aux input, but I never use one and haven't tried it yet. (The pioneer has one on the back, I can plug a cable into if desired later). I ran the USB cord from theback of the new head unit into the little sunglass compartment above the unit, and plug my USB music in there. My sunglasses never fit in that thing anyway!
So, I am living proof that an aftermarket head unit can be attached to the factory amp/speakers/and backup camera. You have to splice an RCA jack into the wiring like Drunken Swagger said earlier, and this whole job was not fun or easy. But it can be done, and it sounds and looks good.
I'll try and attach some photos, as proof it really happened! I was gonna do a full write up on it, but got so frustrated, and took so long, I gave up. I just wanted to let anyone searching threads that it could be done and give the basic items I used to complete the job. The interface modules aren't cheap, and I spent just about $500 on all the bits from start to finish.
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