This code is saying that your catalyst monitoring system on bank 2 is below threshold. The catalytic convertor is not doing it's job, or the emission system has another fault causing this code. Have it tested to ensure of the proper fix.
you can try doing a thermometer test for the catalytic converter (this may be the issue). get an infrared thermometer (from harborfreight or the like), check temp before and after the cat. the temp at end should be hotter than at the beginning of cat. maybe 100 degrees or so. do this once the car is hot. Ive seen the cats on tauruses fail often. just something to check that wont cost a lot to do. and make sure the o2 sensor connectors are good n tight and cleaned (connection side). HTH