Diagnosing electrial issues in EGR-circuit

Greetings,

The car in question is a 2002 Golf 1.6 petrol engine with the AZD-engine code.

The issue im having is a lit check engine light with the code "P0407 - EGR Sensor B Circuit Low" present. See the attached file for a wiring diagram of the sensor and valve which are incorporated in one unit. The whole unit has been replaced by the previous owner but did'nt not seem to relieve the issue, and right now im focused on troubleshooting any wiring/conncetivity issues.

I've watched Pauls video on how to test a electronic EGR valve ( How to test an electronic EGR valve (GM P1406 case study) - YouTube ) and it seems like ths is a very similar, if not the same, set up as the one he is working on. So this is what i got so far:

I've assumed  that "li/ro", "li/gr" and "br/bl"  wires are part of a position sensor where i should have 5v reference on "li/ro", ground on "br/bl" and "li/gr" is the signal wire. With the connector plugged in, key on and connected to ground i found 5v on my reference wire, 0v on my ground wire and about 0,9v on my signal wire. None of this seems to be attention-grabbing (maybe a bit high voltage on the signal wire??).

Now, I've gone on to assume the "li/ws" and "sw/ro" are connected to the solenoid. While connected to ground, key on, with the plug connected and backprobed i found battery voltage on both wires. To find out which one is the control wire i disconneted the plug and found battery voltage to remain on the "sw/ro" wire - this has to be my power feed, which agrees with the wiring diagram ("159" is from iginition power supply). So, I therefore assume that the "li/ws" wire is ground controlled by the computer and would drop to 0 when the plug is disconnected, but it does not. On the "li/ws" wire i found 2v while being connected to ground.

Since im a beginner and have limited knowledge about electrics I would like your help dissecting this. Is my reasoning sound and does this mean that the control-wire "li/ws" is shorted to power or open somewhere? What is the smartest way to approach this? Since the wire is only conected to the ECM and EGR-valve im thinking a shorted connector at any of those two places are a good place to start? 

Thankful for any input on this!

. On the "li/ws" wire i found 2v while being connected to ground

Assume you mean with one lead of the meter connected to ground and the EGR connector disconnected?

Since this wire goes to the computer, and is likely the output control for the EGR valve, the 2v may be bias voltage.
I try not to work on euro cars, so I don't know what bias level to expect on your VW, but that doesn't sound completely out of the ordinary to me.
Hopefully some one who doesn't mind wrenching on these will chime in and offer you some help.