I have a 2001 maxima 20th ann. edition and when i turn my car off there is still an electric motor that runs.?

the sound is coming from the driver side. i pulled some of the fuses to see which circuit it was running on. when i pulled the engine cont 2 fuse the noise stops. idk i was thinking that it is the secondary air intake pump, (smog pump) but im not sure. if so can i unplug the pump and the car still run? or byp the pump and the car run? my car is registered out of state so i don't have to have an inspection but it gets to be a pain when every time i stop and shut the car off i have to either pull the neg battery cable or pull the engine cont 2 fuse.