Hello,
Can someone give me the basic idea how to wire a 2 channel amp in my 02 AP1 to power the speakers only. I have an aftermarket Pioneer head unit that I already wired a year ago to aftermarket Infinity door speakers. After wiring the amp to the battery and grounding etc...do I just plug in RCA cables from the amp to the head unit or do I have to physically run new speaker wires from the amp to the speakers? Thanks a lot!

 

following, in the same situation

 

If you used an when you wired your headunit, the speaker wires from the headunit connect to the speaker wires heading into the
door through this harness. So, You need to disconnect the headunit's speaker wires from the adapter harness, and connect speaker wires from the
amp to the adapter harness in their place.
Disconnect the battery (-) terminal (always a good idea when working on electrical accessories).
Clip the four speaker wires connecting the headunit harness to the adapter harness at the splices, or in the middle if it's a plug&play (Modifry) harness.
While it's unlikely that a cleanly clipped wire will short, it's a good habit to wrap the now unused headunit speaker wires with electrical tape to be sure.
Don't clip any wires off so if you decide to go back to the previous setup you can!
Then splice the amp speaker wires to the adapter harness speaker wires.
Depending on the amp, you may also need to connect a turn-on wire to the headunit's amp remote turn on wire.
Here are the standardized wire colors: