Removed my rear seats yesturday so I could fit something big in my car. Besides being able to hear the gas in my fuel tank move around, I also hear a constant, high pitched noise while driving. Its not very loud but enough to be annoying.

I think it's something to do with the electrical system because it changes pitch slightly when I turn on the headlights. Noise was gone when I put the rear seats back in. Anyone else experience this or know what it is?

 

You could be hearing the fuel pump itself. I had to drive around without my back seat once and remember hearing the fuel pump.... But I don't remember it's pitch.

 

I'd put money on that it's the fuel pump. I think it's right underneath the seat, and if you don't have the soft seat there to muffle the sound, you're going to hear it. It's also very likely that it'll be a high-pitched whine. Nothing to worry about.

 

Is it constant or does it change pitch with speed?

Do you have any aftermarket electronic components installed? headunit, amps, etc?

 

its the fuel pump. SR recently replaced mine due to fuel pressure issues on the dyno. now my walbro 190 (made for late 90's mustangs) is much louder than the oem and even louder than the 255 SR has in his car. the inlet is much larger than the walbros most run for the maxima so i assume that is the difference in noise. i dynomatted the top of the access port and with all the seats in, the whine can still be heard. it is also more noticeable outside the car. the sitting part of the rear seat really blocks alot of the fuel pump and tire/road noise. if you put on your blinkers, you will hear the tone/pitch change with the blinker same with the difference you noted when turning on the headlights.