One problem related to o2 sensor has been reported for the 2000 Volvo S80. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2000 Volvo S80 based on all problems reported for the 2000 S80.
My 2000 S80 Volvo has a defect with the emission control module it was losing power and idling very bad. Because of this problem the cat converter and O2 sensors also miss functioned which cost over $4000 to repair after I got the car back 2 days later the emission message appeared again and the car is not running well.