92 pathfinder

You can test with a 9 volt battery for speaker wires.  If you hear a crackle from a speaker then you know those are the leads for it.  To figure out polarity, you will need to see the speaker moving in and out.  If the cone moves outward, then you have the polarity on the battery correct(positive and negative that is).  If the cone moves inward, then it's in reverse.  Don't leave the battery on there for a long time.  DC current can build up heat in a speaker and the speaker doesn't move back and forth like it will with AC current to keep it cool. 

You can use a volt meter to test for 12 volt constant and ground.  That shouldn't be too hard to figure out.  12 volt constant is for memory of bass/treble/clock/radio presets when the stereo is off.  You can even run your own ground wire if you can't find one cause some cars don't have one.  Chrysler for example.

Then with most of the others eliminated, that should only leave a couple or maybe just one.  That would be the 12 volt switched wire that only has power with the key in the ignition and on.  That's what turns the stereo off when the key is removed. 

There may be a power antenna wire.  I hope not since I don't have a suggestion on that one.  You would be looking for a remote wire to connect your deck's remote wire to.  I don't know what to say on that one without going to a lot of trouble to do a continuity test and you might have to pull out the antenna to do that.  I've never had that problem.  You can look at the antenna and tell if it is power or not.  It would be segmented to retract like old time TV antennas and portable radio antennas, not a solid whip of wire like on most cars.  If it's not power, forget it.  Just plug in the antenna coaxial cable to get radio reception.

Once you've found these, then you got it.  Insulate the ones you don't use with a wirenut and tape, if their are any, and forget them.

Also, you may find a wiring guide here on this site that would be for your car.  Look up at the top of this forum's page.