[PepsiBlueFloat]

these 5 wires are coming from the pioneer stereo or from inside the dash? If they are coming from the stereo it should say right on top of the cd deck on a sticker, or on the instruction booklet what each wire is for EXACTLY. Now, if you're talking about whats coming from inside the dash; unless you've got something like steering wheel volume control or whatnot you should only need 3 of the5 wires. Here is what should be.

2 speaker wires for each speaker (positive and neg dont usually matter) they will be labeled on the wires with LF+ and LF- (left front) and RF+ and RF- (right front) -- just make sure both "L" wires go to the left speaker and both "R" wires go to the right speaker.

Then look at the wires coming out of the dash. If what im understanding there are 5 of them not including the antenna. To get the CD unit to turn on there needs to be 3 different powers going to it. The ground wire (negative). Its a black wire. The other two wires out of the 4 remainging are going to be tuffer to find out which is which if they are wierd colors. Coming out of the back of the stereo there is a yellow wire and a red wire. They yellow wire is always connected to the battery -- its used to store presets, keep the clock right, and settings and stuff. The red wire connects to the ignition switch. When the car is turned on it get power and turns the actuall unit on. Stereo wont work w/o this one. Now; when i say red and yellow wires coming out of the stereo -- they may be different for yours, justlook on that sticker on the stereo. They should be labled with IGN/PWR (red) and BTRY/BTR (yellow) or something along those lines.
you may just have to try all 4 of those remaining wires to see which is which if you dont ahve a voltmeter. The two wires you have left coming out of the dash at the end i have no idea what they might be for since the car ispretty old. But they are not needed for the stereo to run, so if the stereo is working right just cap/tape them off.