Nissan Repair: 2001 Nissan Maxima Service Engine Soon Light, nissan maxima se, nissan maxima

Question
Von
Ok I am going absolutely nuts and my wallet is getting thin. I have a 01 Nissan Maxima SE about a month ago the service engine soon light came on. I went out and purchased a scanner fiquring it is a good item to have. I hook it up to my car and do a scan on it and I get a code for the O2 sensor bank 1 sensor 2. I call up Walker and ask them if they could tell me where exactly that sensor is so the guy tells me it is post cat  on the front side of the engine closet to the radiator. I change the sensor reset the light and start the car no light. Ha about a week later the light is on again I do another scan and you guessed it the same code. So now I change aonther sensor in the same position fiquring I had a defective sensor before.Reset the light and drive no light well guess waht the light is on again but now after I reset it it only last one day and the light comes on. Can you first of all tell me did I change the right sensor to begin with and should I change the other sensor on the same bank, or could I have another problem like with the converter or pre cat and not get a code for it? Any help you can provide would be greatly appreciated and will save me alot of money.
Thanks
Eric
Enjoy your hoildays

Answer
Eric,

First I think you changed the wrong oxygen sensor.  Replace the other one.  Also, fill up with premium and add Lucas fuel treatment as I have not trashed any Nissan fuel systems with this.  Others seem to eat the injectors.  Also, I would replace the fuel filter.