Doug,

Tnx for the comment. Bottom line is that I'm not seeing any of the O2 sensor codes, just P0172, which is system too rich. I did find some non-volvo information which seemed to indicate that one of the possible causes is dirty fuel injectors. Apparently this code shows up if the engine exhaust is richer than the computer thinks it should be based on the injector timing. If the the injectors stick or don't close cleanly this can happen. After reading this I put some Techron injector cleaner in with the last tank of gas. Need a few days to see if this helps.

Dave