Help: Buzzing Electrical Noise

[Delineate]

Would anyone know what does a buzzing noise (sounds like the one you would hear from a a high-voltage electrical line) means whenever I start my car (a 2001 330ci)? I traced where the sound is coming from, and it seems to be coming from under or near the gas tank and/or near the rear axles. Recently, the "Service Engine Soon" light has been coming on and would stay for several days before disappearing again. I don't know if this has to do with the buzzing sound.
Any insight to this is greatly appreciated!

[KC Ron Carter]

Have the dealer correct the Check Engine light.

Ask him to determine the cause of the buzzing noise coming from the location of the fuel pump.

Later,

[Filehorse 525i]

Most likely the buzzing noise IS the tank-mounted fuel pump. It's not something you notice unless you happen to be around the rear of the car when the engine is running.

[323imankiks]

take it to autozone part stores they check the engine light for free. and tell you what code is coming up