To wire your factory system for four channels, see this thread.

https://www.crossfireforum.org/forum...-channels.html


AGAIN, the factory head is two channel, but any replacement you buy will be four channels.
Also, ALWAYS use the speaker lead outputs to drive the car's amp - our amps are not designed for "line level" drive. SOME heads provide the needed drive, but if you use speaker lead outputs, you knwo it will work and you know you will have no issues with noise pickup.