That depends on the amount of pins the old and new stereo have - the "pins" are where you plug your wiring into in the back of the stereo and not all stereos have the same number of pins. (But wiring adapters with the suitable number of pins can be bought)
If you do not have a wiring harness for your after market deck, then go out and get one. There cheap and will save yourself alot of time cutting and trying to match your speakers to the deck
color code of car stereo wiring
http://www.modifiedlife.com/request-a-hyundai-car-radio-stereo-wiring-diagram/
What is the wiring diagram for the car stereo on a 1997 Ford thunder bird
colar code for sony stereo car
http://www.modifiedlife.com/car-stereo-wiring-diagrams-and-car-radio-wiring-diagrams/this is the best site for diagrams for stereos, enjoy!!!
http://www.modifiedlife.com/2005-hyundai-accent-car-stereo-radio-wiring-diagram/
Car stereo wiring color codes for a Mustang can be seen on a diagram. The diagram may be found in an owner manual or request from the stereo company.
http://www.modifiedlife.com/1993-pontiac-bonneville-car-stereo-wiring-schematic/
No its impossible!
Bad wiring connection or internal wiring connection in the stereo
kenwood car stereo kdc-mp528 wiring diagrahm