2004 chevy tahoe remote turn on wire

Hello everyone, I have a friend with a 2004 Tahoe for whom I'm trying to install an amp and sub. He does NOT have a stock amplified system, navigation, DVD, etc. etc. He just has the stock CD player and speakers. The only problem I'm having is with the remote turn-on wire. I tapped into the stock amp turn-on wire (small orange wire) on the head unit wiring harness, but it didn't work, and I have no idea where else I could tap into. I read that you can use a relay with pin 87 getting constant 12V, pin 86 12V ground, pin 30 12V output (I'm assuming this is where the remote signal would come from going to the amp), and pin 85 low current 12V input from the HU. Can I use the stock amp turn-on wire (small orange wire) that I previously attempted to tap into for this low-current wire? Will this work, or is there another wire I can tap into to get the remote turn-on signal? I've also read that there's a dark green wire behind the driver's side kick panel that is a 12V accessory lead. Will this work? Any and all help is greatly appreciated. Thanks!

I would just tap into an accessory wire from the ignition harness and run it right to the amps remote turn on terminal.

Use the ignition harness.  Take off the panel below the steering wheel and toward the bottom left you should see a wire harness with several fairly thick wires (about 12awg) in it.  The dark brown one can be used as a remote turn on.