I recently bought a used Honda Civic 2004 LX and I noticed that only the driver side speaker is working. I tried upgrading my passenger side speaker with aftermarket ones, but they aren't working. I've checked the speaker cables and they seem fine. Researching online, I found that there's no specific fuse for the speakers, and suspect it could be related to the radio unit since I'm still using the original factory radio.

Additionally, I've noticed that my rear speakers aren't working either. How can I troubleshoot this issue further? Any suggestions or similar experiences with Honda Civics would be greatly appreciated!