Mystery feedback buzz
 

I have a 2004 Honda S2000 39k miles. It is bone stock except a tenabe medallion touring exhaust, berk high flow cat, and aem v2 intake.

When the radio/cd/aux is on i have a buzzing feedback coming through the passenger side speakers (both large bottom speaker and top tweeter). I tried swapping the speakers with the drivers side and the feedback continued through the passenger side door (with the drivers side speakers in it). So it is not the speakers. When the headunit is on volume ‘1’ there is no music just feedback buzz. It does change pitch with the engine rpm but very small amount. When you put the headunit on ‘mute’ or turn it from ‘1’ to ‘0’ the feedback buzz goes away. With the headunit off there is no feedback buzz.

My question is if replacing the headunit would eliminate the feedback buzz or is it just a frequency the speakers are picking up maybe from the engine or exhaust? Is there a ground for the passenger side door somewhere that could be bad?

Thank you so much for all the help. I’m fine changing the headunit if it’s the failed or failing part but dont want to waste money if changing the headunit wont fix the issue.

So with ACC on, but engine off, you get no buzzing through the speakers?

That's correct. Only when engine is running I get the feedback/buzz

I'm going to test the altinator and battery. If those check out I'm going to try to ground the battery to the chassis in a second spot . I'm still
guessing the headunit is on it's way out