Could any one give me some suggestion to diagnose this high pitch noise issue please?
The noise coming from the rear end whenever I start the car. The noise is not loud and does not change when the car is under acceleration and at idle.

I had my car checked in a dealership. The mechanic only opened the fuel filler door and put his ear against fuel filler cap and then told me that the noise does not come from fuel pump. He said it was an exhaust noise which is normal.
My question is that whether the fuel pump noise can be so easily excluded without any other check?

 

It could be an exhaust noise. If you put you ear against the bottom of you back seat and hear the noise louder, then it is more then likely the fuel pump. Honestly, my gut is telling me fuel pump.

 

Thanks Andrew!

I put my ear against the right side rear seat and the leg area before the right rear seat, I could not hear any noise.

I opened the fuel filler door and the gas cap, put my ear against the hole, and I could hear a tiny high pitch noise by which means the sound is not as loud as I can hear around the car.

 

I hear a whistling sound when I move the wheel