HEY don't waist your money on a new 02
Take it out, wire brush it very good and stick it back in.
If you have a OBD2, clear the codes, if not drive it for a while and the codes should go away.
Truthfully -Volvos are notorious for codes, so it's a good investment. then search the codes on google.
save yourself some bucks-- what happen is the carbon builds up on the sensor, making it hard for it to monitor the emissions.
