Hello can anyone please help me with this. I added an after market stereo. Still have the original installed. I have 2 amps hooked up to it. One for my subs and one for speakers. I still have the speaker wires from the new stereo not plugged into anything. I'm wondering if I could use them to get the stock amp to play through the new stereo. Thank you.

If I remember correctly the stock amp has very specific specs that may or may not work with aftermarket speakers or radios. But based on what I remember from my audio days in the early 2000's, connecting it won't hurt anything - worst case it won't work.

i still have my original HU and have 2 amps with subs. I used the FSM for details on the wiring since it was a little tricky using the stock amp. i bypassed the stock amp all together since i was using my own amps. i would take a look at the FSM for the HU diagram. it is comprehensive but shows you all the details you need. good luck

To make sure I understand, you want to output your HU to the stock amp? My question is why...the stock amp is crap. Either way, it depends on the ohms of your system and the ohms of the stock amp outputs which you can check on the back of the stock speakers. I don't remember if the FS manual specifically states the ohms of the system. Off the top of my head I think it's 4 Ohms.

But know when you do that you will lose all voice feedback from the car (navigation and whatever else talks), unless you build in a switch.