Bet this will stump everyone!!!! voltage disappears when head unit plugged in.

[2004tundra]

ok, so here's an update. Im a retard, and now I understand why the harness I bought didnt match up. I just realized toyota put a little factory amp in there that I couldnt see and I had the wires that came from the amp to the factory radio, now the harness I bought matches up. Thanks to all of you for trying to help me, I really appreciate it!!!!

 

[1aespinoza 10+ year member]

. I just realized toyota put a little factory amp

Dab gummit! Now we all know something new. Thanks for the update.

 

[hispls 5,000+ posts]

a little factory amp

Yeah, that's a wild card. Stuff like that is why unless you really want to use all your own wiring you use Crutchfield or similar to figure out precisely which METRA kit you'll want to integrate.

I'm still concerned about your <12V resting voltage though. 12.6 charging is not enough to properly maintain a lead acid battery. Might want to do some digging there and see what's going on with that.