Left Front Speaker intermittent and no signal sound
I have the exact same problem as you. Intermittent left front speaker. No crackling, no buzzing....either perfect, or nothing. I have moved the wire boot on the door all around. If it were a wire problem, it would have cut in/out, or crackled or something. I'm thinking it is in the sound system, and must have something to do with the circuitry that makes the turn signal noise. I'm thinking I could have a nice aftermarket stereo put in for the price of a diagnostic from the dealership. It drives me nuts though. I'm only about 40 miles north of you. Maybe it's an Indiana Cobalt thing?
Let me know if you find out what causes this.