I've been meaning to scope one of these working & not working - do you have a scope?
If so I may get chance tomorrow to test a working unit & post a pattern for you to look at.

The sensor uses some form of digital signal transmitted via one of the sensor pins, which it passes through the coolant & is picked up by the other sensor pin & broadcast to the dash insert.
That's as I understand it - I stand to be corrected.

But that aside, we specialise in VW & change plenty of these each year, 99% success rate so far - we had one that was a dash fault, all the others were cured with new senders.

hth,
Jon.