what was everything that you installed?

if you got a new head unit / new stereo you'll need to connect the remote wire (usually a blue wire) from the new unit to the stock amp as well as your new amp...

I upgraded to a new head unit, new amp and subs. Of course all the wiring that's involved as well. I had previously had an aftermarket deck in there, I copied the wiring that they had to setup the new harness for the new deck. The blue/white cable on the harness has a cable that goes to the stock amp and that's were I connected my new amp as well. The blue cable on the harness has a small label "Pwr Ant". I'm kind of guessing at this point and don't want to blow any fuses or my amp! Should I try to hook it up to the "pwr ant" blue cable?

If it label as you describe and can use ir for power/remote on control for ampliers.

well... got it figured out... Got my amp and subs going... dang my stereo sound good!!! The stock speakers sound really good with the subs. I've got a lot more bass and the subs don't take all of the space on the back of my vehicle! Thx for all the suggestions and tips guys! Learned a lot from this little project... Now I just need to install the bluetooth adapter for my cell phone!

what did you end up doing?

I had the wiring correct initially. For anyone else that is wondering it's on pin #17. That's the remote turn on. My issue was the ground. I wasn't grounding the unit well. I grounded the amp to the base of the seatbelt and voila... the amp turned on just fine.

Thanks for an awesome write up! I ended up going through the grommet under the battery. I noticed there is a fair bit of heat shielding there and wondering how hot it gets... should I be protecting my power cable in the engine compartment? If so what would be the best way to go about this?

I have a related question. My previous Ti had a head unit that could be powered on without the key in the ignition. I really liked this setup (even though I had to be especially mindful of turning OFF the unit after a drive to not kill the battery) but the sacrifice was well worth it!

I also really liked that it stayed on while I started the car so head unit didn't reset and I could avoid the delay in reconnecting to my phone. Can someone recommend the safest way to wire it for this?

My initial thought was to just connect both the red/yellow from the head unit to the same constant (yellow) wire coming from within the car. Upon further reading it sounds like this circuit isn't always rated and fused appropriately for the full draw used by the stereo system.

I figure now that I have that lower battery grommet exposed it would be relatively straightforward to run an independent wire to power the the unit direct from the battery (with an inline fuse near the battery) If going this route would it be simply disconnecting the yellow wire and re-connecting it to my direct battery wire?

One other thought, I've noticed when a vehicle is being started generally all other circuits are cut. Is there any risk of power spikes during this procedure ruining my audio system if I were to wire the head unit direct?