I have a 2002 Maxima with the original radio and speakers. I have a cassette player with a aux cord and only the left side speakers work when I plug my phone in. When I put FM, they all work. I need help fixing this, thanks.

 

Process of elimination...

Assuming the headphone port on your phone works, try a different cassette to aux cord.

 

I bought a new one and it worked the same so I tried it on another vehicle and all the speakers worked. So it was my car that's doing that. I cleaned the magnet digitizer and it still didn't work.

 

Sounds like its time to replace the radio. Your speakers and your ears will thank you when you do.