Ok, my car threw the code P0155. The screen on the Cen-Tech CAN OBDII reads as follows:
01/02 and P 02/02
The "P" comes up with 02/02.
It's apparently bank 2 sensor1...does that mean drivers side or pass side of the car? It must be "pre-cat" right?
Are our sensors pre-cat and post cat sensitive?
I'm looking to buy either NTK or OEM AcDelco.

Any help is appreciated.
(mpg's and driveability is obviously suffering a bit)

 

bank 2 ----sensor 1

pass side - pre cat


the o2 sensor is either shorted to gorun, shorted inside or the the heating part of it is screwed up, check for a short to groun ( like melted to the pipes) if not i would suggest replacing

 

Thank you for the feedback. The car has over 105k miles on it...it couldn't hurt to just replace both (front pre cats 02's).
Summit has this, I believe its the right one:

http://www.summitracing.com/parts/NGK-21528/?rtype=10

 

My car threw this code when I first bought it and I just cleaned the MAF,Throttle body, and replaced the air filter. That cleared up the problem for me you might want to try that first