Sub not working

[JoshMarshall]

Hi guys just joined this site.
Cut to the chase I just brought a 03 fiat punto active sport and being 17 and it bein my first car I wanted a sub but I discovered I had a built in one only problem is that it does not work, there is a aftermarket stereo in the car
All help wanted any body had same problem know the fix tell me
Thanks josh

 

[PuntoHowTo]

i believe it is powered off an output from the standard radio, you need to find out which wire this is and reconnect it to another power supply