Originally Posted by kmarei
You need a special harness sold by forum member Technic
You plug it into the amp
And the plug that was In the amp, plugs on the other end
That gives you RCA out that you can plug into the amp for the sub
And keeps all the speakers powered by the amp
You do not need a special harness or anything. I tied right into the factory amp with speaker wire taps. I can't find the wiring diagram we used but it's floating around the internet. We tied the speaker wires into a line level converter and poof, you have an amp + sub tied into your factory system. Took 2+ hours and a 6-pack of beer.