I have an 2008 Accord and sereral weeks ago my radio started an oscillating sound around 6o0HZ. This happens only on AM signals and only after the engine has been running for about 20 minutes. The engine speed doesn't seem to affect this noise and the signal clears up if I turn the engine off.

I think a noise from defective plug wires would change with the engine speed. I'm thinking some kind of sensor maybe???? Anyone have any ideas.

Thanks for any help,
Bill

 

very odd problem. maybe the antenna wire is too close to the ECM/PCM?

you could pick up a noise filter and manually insert it in-line with ignition power... or use an oscilloscope to probe and find which wire that signal rides on.

 

Thanks for the input,

The fact that it doesn't do it when cold makes me think some part a little funky, I'm thinking of hitting some parts with some "circuit cool".

I do have a scope but don't know if I'd be skilled enough to trace it that way. The antenna feed is from the rear window, I'll see if it might come close to engine.

Thanks, Bill

 

since it only does it when it's cold, it could be something in the ECM/PCM as well.

Most likely, it's an issue inside the factory head unit. Some freeze spray would be a helpful tool, but it will be a hassle making that happen. you'll have to remove the factory radio, remove the cover, reconnect the factory radio, let the car worm up and let the problem begin, then freeze the board.