I picked up a Pioneer AVIC-F700BT, it was a deal so it was missing the preamp wire harness. There are times when you find a cheap car stereo missing a few accessories (thats as much as I'll say about that). When you do, you'll need a wire harness. I thought it would be helpful for certain people to write a how-to on making your own.
Step 1: Starting Out
This is the port that we need a harness for. It has 12 pins and handles the preamp outputs of the stereo for connection to an external amplifier. The harness for it would come in the box if this unit was bought new.
The first thing you need to do is find the pin-out diagram to tell which pin handles what function. These things are available all over google for whatever port you might find.
What else do you need: Soldering iron, glue gun, continuity tester, shrink wire, port connector, female a/v jacks