Volvo Repair: Rear Oxygen Sensor, oxygen sensor, volvo s70

Question
Hello Roger!
I have a 99 Volvo S70 and have 40,900 miles.  What could cause rear oxygen sensor to go bad?  It caused me about $500 to get it replaced.  Is this reasonable?
Thank you.
Renee


Answer
Renee, thats a bit steep but not too far out of line.   02 sensors are pretty much wear items.  Some last a long time, others fail within the warranty period.  I doubt that would have been covered under the warranty but I think the emissions warranty was 7 years.  Hope this helped.  Roger