I have a 2007 Fit LX, and all of a sudden the AUX input got really quiet. If I turn the stereo volume up to the max I can just hear it, otherwise nothing. This is a factory installed AUX input, nothing aftermarket, and I made sure the volume on my iPhone was at max. I wonder if there is a preamp that is dead? Has anyone else seen this before? Any solutions?

 

First thing I'd do is hook up a different source to your AUX input to verify it's not the phone output having issues.

So assuming the phone output isn't the problem, need to see whether it's an input-specific problem or a global problem. Are the other sources at normal volume with no issues? If they are, then my best guess is a bad circuit inside the head unit or the wiring to the head unit causing problems with your AUX input.