2012 Tacoma Audio Issues

Recently developed a new issue with my truck. Stock setup, non JBL. Rear speakers have quit working all together, Bluetooth only comes out of Driver Front, radio/aux/cd comes out of Passenger Front and just slightly out of Drivers Front. It’s a new issue, started in the last week or two. I’m not sure where to begin with it. I checked fuses and they look ok. I’m sure I need to check all wiring, but have no clue how to get into head unit and beyond. Anyone have any advice or experienced something similar? I can work on things myself so I’m sure I can do it with a little guidance. Thank you!!

 

Thats an odd mixture of problems. I would check my ground first. To get behind the stereo is pretty easy. I take the knobs off my hvac controls. Grab the two outer posts underneath knobs with pliers and yank back towards you. This should expose four 10mm bolts. Remove said bolts and yank stereo towards yourself. You can do quick ground check from I believe its a 10 pin white plug going into radio. Its only black wire on that plug...from menory its lower row, middle wire.