Help! Check engine light
 

My car is at 23K miles and recently I got a check engine light and went to Autozone and get a OBDII diagnostoc scanning tool and read the DTC and here what is on it

Error code:
P0141 on the scanning tool
" 02 sensor heater circuit malfunction"
(bank 1 sensor 2)

So I am assumming it is the rear O2 sensor on the catalytic converter. I went to the car check the connection make sure it is good and pop out th shifter console where the O2 sensor leads to the connector near the shifter and it is all good. So I tried to clear the code on the scanning tool but it is still there I guess it is a hard code stored in the ECU unless it is fixed. Do you guys know if the O2 oxygen sensor which is part of the exhaust system from what I know it has a limited lifetime warranty or something like that this is covered under warranty? I called a couple of dealers and the 02 sensor cost like $250 or so which I don't want to spent out of my own pocket and they don't have them in stock. I also noticed my gas mileage is like crap and I know for a fact it has something to do with the sensor.

It'll be covered under warranty. Unless something like a rock or something somehow messed it up (highly unlikely), they'll cover it.

The crap mileage could be likely to be caused by the O2 sensor.