floatplane

I have an 04 Runner and I am trying to put in an aftermarket head unit but stuck right now becuse I can't find the negative speaker signal wire. I was wondering if anyone might know what color it is / or what pin is the negative speaker signal wire?

I have the JBL upgraded system and the metra wiring harness I got for the 04 (metra 70-8113) does work except for that negative wire. I called metra and they said that they learned that Toyota moved the negative speaker wire in the 04 compared to the 03, and they don't know where to. I thought it was funny that they know this but still sell the harness when you ask for an 04.

Any help is greatly appreciated as my ride sits in a garage in pieces.

Thanks all,

Float