I got a Pioneer HU, pulled out the stock stereo, started soldering the harness the shop sold me to the wiring on the head unit.

There's 4 male connectors that connect into the head unit, but the wiring harness only has two female connectors... So I said eh, I'll try it... Basically I connected the antenna power converter (and soldered the red wire off that to the accessory wire), and connected everything by color code + manual checking.

I go to plug everything in, slightly dubious it will work since two of those male connectors are just going to be hanging there, and lo and behold sound is only coming out of my front right speaker. The Pioneer HU turns on and everything, it's just that the sound only comes out of the one speaker. Didn't test the six CD changer.

Anyway, here's the question... Did I pick up the wrong wiring harness, or did I just solder/connect the wires together poorly? If the wiring harness is the right one, what is with the two extra male connectors? Just leave them hanging?

This is the harness I got:
http://www.crutchfield.com/S-hD1WrK0WySH/cgi-bin/ProdGroup.asp?g=103000&avf=Y

Those four male plugs go into your pioneers RCA outputs. It sounds like you have a deck that only has one set, but still doesent explain how only one speaker works. There should be only a few connections that you would have to soldier anyways, Constant power (Yellow), Switched power (Red), Ground (Black), Amp turn on (blue with white stripe) and maybe an illumination wire (orange) if your pioneer deck even has one. The other wires on that harness should be 4 seperate RCA connections that will plug directly in to your pioneer deck... if it has 2 pairs. The correct harness should be a Metra 70-1787 and if you want your AM to work you have to buy a antenna adapter Metra 40VW-54. Take your car to a reputable stereo shop if this doesnt make much sence to you. Good luck.