ok, so I know this post is pretty old, but I thought I'd reply anyway. I don't have any answers, but have the same issue. Check engine light came on with the same code. I had the code cleared at an Auto Zone and replaced the gas cap. The light stayed off for about 3 weeks when it came back. Read the same code and cleared it again and it has not come back for a few days.
They said there could be a small vacuum leak somewhere, but that sounds like it could be pretty tricky to find. Anyway, I figure if/when it comes on again it will be a trip to the dealer unless anyone else has some ideas to share on this?
Oh yah, 98 V70 non-turbo with about 105,000 miles.