code P0141 possible o2 sensor issues??

[5arge]

The issue is my car isn't going through gears properly. It'll go thru 1st and 2nd fine, but went it gets to 3rd the rpm gauge just runs high and never drops back down. This is an automatic transmission by the way. But the thing is I can go any amount of speed I want therefore I doubt it's the transmission. I had the same issue happen awhile back and it was a "solinoid"(sp) pack that works with the transmission and when a shop looked at it they even said then it wasn't my transmission just the silenoid pack, which they replaced and it's been fine.

But now, its doing the same thing and the check engine finally kicked on. SO jus for shits and giggles I go to Autozone to see if I get the same error code as last time(which I forget what it was), but was suprised to get a whole new different code of P0141 which is something about the o2 sensor "bank 1, sensor 2". So my question is 2 things...

1.) Is bank 1 sensor 2 the one at the front near the downpipe or the one toward the middle under the car further back?

and ...

2.) If it is a faulty o2 sensor or wiring in that nature of some sort, why would it do the EXACT same thing as far as how it's not shifting through 3rd like last time(is that something an 02 sensor would do)?