I have a 1991 f150 and the stereo was already removed when I got the truck. The stereo that I'm putting in has 2 wires for each of 4 speakers. So far, here is a list of wires that I have figured out what is:

On the Plug
Green/Yellow - constant hot (memory)
nothing
Yellow/Black - switched power
Blue/Red - Illumination
Orange/Black - Don't know
Red - Don't know
nothing
nothing

Loose wires that I don't know what they are for
Orange/Green
White/Green
Black/White
Black/White

I guess if I just knew which wires goes to the speakers and which one is the ground I could get it hooked up. Thank you for any help.

 

Go to http://www.bbbind.com/tech_database.html and drill down to Interior/Driver Amenity then Entertainment and it'll give you your wiring schematic.

 

Thank you Carolina Five-0 that link was VERY Helpful!