Thanks guys-- I ended up getting the PAC unit anyway. Like you suggested, I'm going to try wiring directly to the vehicle harness 1st, then see what does and doesn't work. Then I'll connect the PAC and report back exactly what changed, just so we all know for the future.
Updates in a few days--
You mean you are going to wire the radio harness to an adapter harness to plug into the vehicle wiring at the Radio Connectors?
I strongly suggest you do NOT wire the radio harness directly into the vehicle wiring, NOT only will it be really hard to do, you'll make a mess of your vehicle wiring and future radio upgrades or returning back to the original factory radio becomes an even bigger mess.
The adapter harness is well worth the money, its only a few bucks, then you can splice it together with the radio harness comfortably at a bench, then just connect the connectors when you get to the part of shoving the wires in behind the radio.
NOT to mention adding the PAC later, then you just have to pull the harness and cut the wires and resplice from a bench, intead of your hands working in the cramp space inside the dash. Look at it this way, if you paid $70 for your PAC unit, it saved you $20 for an adapter harness, so you only paid $50 for the features it will retain for you.
But according to what you've told us, the only features you have that the PAC unit will retain, is the delayed shutoff, which is nice, but worth $50? If your Pioneer head unit has video abilities, then it will have a parking brake safety interlock, the PAC unit will save you the hassle of having to route and splice that wire, just splice the parking brake wire to the PAC unit's harness and it will simulate for the radio the same signal on that wire when the CAN network tells the PAC unit, the parking brake is set or off.
Heck, most of the PAC units come with an adapter harness, if you did NOT buy an adapter harness, and your PAC unit has one, then just go ahead and put the PAC in right away to use its harness. You can look at this way, if the PAC