I just replaced both of my o2 sensors on my 97 850. I bought the parts at FCPGroton (yes, they DO have the best prices). Both parts cost $245 w/S&H. I'm definitely no expert mechanic, but I do most of the basic maintenance on my cars. I was surprised at how easy the sensors were to install (just make sure you pry the red side clamp open on the connectors). Also, the sensors did not ship with the pigtail you have to use on the front sensor, but FCPGroton sent me one Priority Mail at no charge (thanks guys, if you read this). I had to take it to the dealership and have them reset the adaptation after I put the new ones in, but I still came out about $275 cheaper than allowing them to do the complete installation. Hope this helps. Good luck!

I would just go to FCPGroton.com and order the two online myself and install them at home. Only takes a wrench, even an adjustable one. They are $115/$108 at FCPGroton. Good luck....... Mike

Had mine replaced on my '94 850 turbo wagon about 2 weeks ago & it cost
$435 at an independent Volvo garage. If you don't get it done your emissions
will be high and(I'm not completely sure about this), your car will let unburned
gas go into the catalytic converter which ruins the converter which is big $$.
Don in Denver

Usually if you get a front O2 sensor failure it will automatically give a rear failure. I would try to replace the front only and see if that solves it.
Also check your vacuum lines first

the price that was quoted for you is a little high considering that you can get the 2 sensors for around $225 and find somebody to do this anf will probably charge you for $150 labor and these prices is way off the amount that was given to you.

I just did mine last night bought the parts online to www.thepartsbin.com or myvolvoparts.com or newandusedvolvoparts.com and most of the time you will get a free shipping on these and installed this by myself, I am not experienced on this but determined to save and know more about the car. I put the front car on the ramp and work underneath. I am a small guy so I squeeze myself and take out all the plastic clips then the detach the connectors which is a little bit hard to reach because of the tight spaces but managed to lift the red plastic lock and pull the socket. You have to be patient on this kind of work if not find a mechanic anywhere who will charge you less labor charges.

ChrisQ 97 855 t5