Using existing factory sub with aftermarket head
 

I have a 2002 ES AWD with a factory 7 speaker system. The Factory head unit is failing me so I am planning on replacing it and I want to continue using the factory sub. Has anyone done this and can offer any advice? I ordered a Metra and Scosche harness and I plan to keep the one will do the job best. From what I read it looks like I need to connect the sub out from the factory to the new head unit somehow. I'm trying to get some better directions for it.

Thanks!

There are no audio feeds direct to the sub from the head unit wiring, there is a wire to turn the sub amp on but it seems to take the audio from the rear speakers and filter/amp to the sub from there.

In theory you could maybe run dedicated sub audio from the head unit and use it to replace the audio feeds piggy backed off the rears but you would need to work out which wires at the sub connector are the audio and work out what level they are, I'd assume speaker and not pre-amp levels but you would need to check and wire/setup accordingly...