Thanks tmannian for your advice.

Finally, after four years of driving around with this stupid PO453 CEL on, I was able to first, locate the fuel tank pressure sensor by removing access panels from the trunk ('98 V70R) instead of listening to two Volvo indy shops when they told me that the tank would have to be dropped. Second, I needlessly replaced the sensor to the tune of ~$200, and third I finally determined that there was no resistance on the middle ground wire.

Then, yesterday I was somehow able to trace the wires from the fuel tank up through the right hand side and underneath the dashboard. There I saw a bunch of wires going up, was able to locate the ground wire, slightly pulled on it and it just came down because it had been sheared clean through! Somehow the wire must have been rubbing on something up in the dashboard and after years just cut through. So I was able to splice it back together by finding the other end and presto, all is well and no more PO453.

That, in addition to the VW air pump that I just modified and put in, I am CEL free and can go pass emissions.

Cheers,

Wes