Since you do not have manual hub differtials you are hearing the electric motor dis-engaging the front diff from the drive shafts and trany...
The 2001 Toyota 4runner OBD 2 port is under driver side dash next to kick panel
The 1999 Toyota 4runner OBD 2 port is under driver side dash near center console
Under the engine block !
under the intake manifold
The 1998 Toyota 4runner OBD 2 port is under driver side dash left of steering column
The 1997 Toyota 4Runner OBD 2 port is under driver side dash next to center console
It's located behind the glovebox, up under the dash.
L/H side under distributer cap in my standard
On my 89 4Runner it is under the kick panel on the driver's side.
On the V6 it's on the left frame rail under the driveer's seat.
I believe it to be the airbag (passenger) making that humming sound
The fuel filter 4runner v6 sr5 is located under the car, underneath the the front passenger seat behind the chassis..