Post a capture so others can see.
But you expained it already.
Power and ground. PWM control from ECM and digital feedback to ECM. Duty changes in relation to valve postion.
Signal is generated inside valve by little electronics module.
There is info out there, Autodata, Bosch ESi & Tis. Pin 2 comes from a fuse, 3 goes to earth. 1 & 4 go to the controller.i can't find any decent information anywhere.
You don't say what Fault (code) you have, but I would have thought (for EGR) that Live Data & Component Actuations would initially be your best friends here.
A good scanner will have EGR Command, Pulse Duty, Reply & Air Mass and an actuator function.
You could (with powers & grounds confirmed) have the scope on pins 1, 4 & MAF signal, Amp Clamp on 2 or 3 as you actuate it for the pretty picture.