I hear a knocking in rear inside panel, just under the door locks... on 2002 Ford Explorer

it is not the door locks, it starts the minute you put the keys in the is behind the panel...what could it is NOT the lock is below is electrical and behind the plastic panel on drivers side next to the third seat.

Asked by for the 2002 Ford Explorer
there is a fuel pressure sensor there but it should not make noise. have a shop listen to it to identify the noise.

we noticed the sound gets louder when the rear heat/ac is turned on...and softer when turned off....doesnt go away completely....we found it is a damper door actuator that had gone bad, thanks for helping by giving me an idea of what it might have been, I learn so much from chat lines like this, once again, thanks!