Did you look at the discussion of oxygen sensor related codes on Bay13? The one you have might be the same as one that is called something like "front heated oxygen sensor, slow response". I got such a code on my 95-850 around 100K miles. I replaced the oxygen sensor with an OEM sensor and the code has not come back in 2+ years. I gather from various posts and other info that the sensors can get sluggish after about 100K miles or so, even if there is no actual problem with combustion. Some other heated devices like gas range igniters and thermocouples also seem eventually to get tired of working.

Though unlikely, a person may drive over something that snags and cuts the sensor wiring. That would probably be obvious once you look.