2015 Rear Speaker Output Question

Hello guys. New to the forum and new to the Tacoma. I have a 2015 access cab (so yup dumb ceiling speakers) with the non jbl head unit.

Call me crazy, but I do like the stock head unit so I would like to keep that for awhile, but don't like the rest of the system. I would just like to add a line out off the rear speaker lead to a 5 channel amp that will run upgraded door speakers and a sub.

Does anyone know the rear speaker wire colors and what harness they are in? Do you splice them or did you use a harness?

I have searched this all over the place and got a lot of good tips and tricks moving forward, but can't really find a answer on how people added an amp to the stock head unit.

Thanks for the help

 

if you do not have the amp yet id suggest getting an amp that will allow a high output signal. if you want fine tuning save ur $$$ for a processor

 

No amp or components yet - just starting the planning process.

 

I believe the plug with the wires running to the rear speakers is behind the drivers side A Pillar trim panel.