One problem related to o2 sensor has been reported for the 1999 Volvo S80. The most recently reported issues are listed below.
This car has several recurring problems that I have never seen on any car before. 1) electronic throttle has been replaced 2 times as well as oxygen sensors. 2) suspension parts replaced 3 times, ball joints, struts, strut mounts, frame bushings. The car still squeaks.