Got my headunit installed and just wanted to clarify what works and what doesn't...
When I wired it up, I wired remote turn on wire from the Pioneer harness to the remote turn on wire (blue w/ white stripe) on the factory connector from Walmart. When we plugged in the radio. No bass from the sub...the signal comes from a speaker line out adapter or whatever so you don't have to mess with that. So my problem was that the remote turn on wire off the headunit, was NOT turning the factory amp on for the sub.
After my friend screwed the wiring up twice (me catching it both times after the fact), here's how you need to do it:
You need to take the remote turn-on wire from your headunit's harness (or if you have a power antenna wire, you can probably use it too I'm guessing) which is blue w/ white stripe, and run it to the POWER ANTENNA wire on the harness (solid blue wire), NOT the remote turn-on wire. This will power the amp on properly so your sub will work.
With my Pioneer headunit, we also had to remove the security bolt bracket from the dash as the bolt was considerably larger than the screw that goes in the back of the headunit and for some reason it was blocking us from pushing the headunit all the way in (even though the depth was the same as the factory unit...wtf?). On top of that, the strap in there (attached to the headunit via the security bolt in the back which is a 3/8" bolt in my 2002, not a 10mm as I read in another how-to) MUST be attached to the grounding screw on the headunit as the headunit will not power up...even if your grounds in your wire harness are connected together.
Just some future info for anyone else doing this...might make things a little easier for ya. I thought the how to I read said there's only 2 screws holding the center dash bezel on...up top. But there's also a screw behind the ash tray that needs removed.
Then the headunit's bolted in with 2 3/8" hex head screws in the top right and bottom left corner, plus a 3/8" hex head screw on the back of the headunit.