2. Any idea what wire I could use for my amp remote turn on?
On the 10-pin wiring harness, there's a gray wire that goes into pin #3. The wiring diagram (
http://www.toyota-4runner.org/5th-gen-t4rs/140402-anyone-has-wiring-diagram-nav-entune.html) calls it "radio ignition". I used this wire for the remote turn-on for my Kenwood compact amp.
I didn't cut any of the wires on the factory harness. Instead, I purchased a wiring harness and a reverse wiring harness from Amazon.
https://www.amazon.com/gp/product/B00009UHKW/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B0007KK2LK/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1
There are 2 connectors in each package. The 10-pin connector has the front speaker wires and some others for power, etc. The 6-pin connector has 4 wires for the rear speaker. I read somewhere on this forum that if I used the connector for the rear speakers, I would lose the functionality of the head unit lights. So, I didn’t use it.
I connected the wiring harness (WH) and reverse wiring harness (RWH) wires together using butt connectors: yellow to yellow (12V battery constant), black to black (ground), black/white to black/white (factory amp ground, I don’t think this is actually used), blue/white to blue/white (factory amp remote turn-on, I don’t think this is actually used), orange to orange (illumination dimmer), orange/white to orange/white (illum dimmer), orange/black to orange/black (illum dimmer ground), and brown to brown (mute, I don’t think this is used).
The red wire on the WH & RWH is called "12V ignition switched". I spliced in the “power control” wire from the sub to serve as the remote turn-on for the amp.
For the white (left front speaker +), white/black (left front speaker -), grey (right front speaker +), and gray/black (right front speaker -) wires, I spliced in the speaker wires from the sub. Again, I used butt connectors to connect the wires to the WH and RWH.
That’s all the wiring. Plug the RWH into the head unit. Plug the factory wiring harness into the WH.
Voila! All hooked-up and no factory wires cut! This makes it nice if you ever decide you want to make changes to your system.