S80 Oxygen sensors
 

I have a 2000 S80 2.9 that has been sitting for over two years while I waited for my grandaughter to begin high school. Well the time has come and I cleaned it up but while driving I got the P0137 and P0161 codes for both downsteam sensors. My thoughts are it can't possibly be a coincidence that they both failed at once so I wanted to ask ya'll opinion.
Thanks
Bob