For a couple more months than need be my CEL has been on. I ran my Laptop Diag from OBD-2.com and code P0141 came up. After then checking each individual sensor for a reading using the software I found that OS12 which I assume means bank 1 sensor 2 , had a reading way below the others @ .03v ( somethin like that). Which sensor for sure is this, and does that reading mean it is bad?

Bank 1, Sensor 2 is passenger side, second sensor (furthest back).

If it is bad enough to keep throwing the code, it is time to replace it.

I checked again this morning the voltage readings... both the after cat (farthest back) O2 sensors are reading really low... Does this mean their both bad. Between .03-.08V or .003-.008v, cant remember...but low readings.

I had a similar problem and this article helped a lot.

http://www.findarticles.com/cf_dls/m0BQA/7_80/77195162/print.jhtml

PS. I cleaned my MAS, cleared the code and haven't had the problem since...

Good luck.