Got the code for O2 sensor AGAIN!

A couple of weeks ago received the code( I think it was bank 1, sensor 1 low voltage) for the first o2 sensor. I replaced the one in the engine compartment and right away it seemed to run much better. However recently it seems to have gone back to square 1 again. I have the same code and whenever I go to step on the gas hard(highway driving) it sounds like it is going to start sputtering again. By the way, the check engine light is on again.
When driving around town it seems okay, but if I get it going and try to pass someone it sounds like crap!!!

Any help would be great

It would help to post the specific DTC you are getting since there are more than one 02 sensor diagnostic trouble codes that can be generated.

Thanks for the reply! The code is P0135 bank 1 sensor 1 . I took a look at he wiring harness and could not see any problems( tough to see though, the wires are wrapped up pretty good)

Thanks for any more help

Just an update. It seems that the car runs fairly normal at city speeds. It idles well( no fluctuations) I thought it may be a catalytic issue however, there is no odor for one thing.
I do think the gas mileage has gotten worse. It definitely is sluggish and doesn't feel/sound good when trying to merge or pass at highway speeds. When I was at the exhaust it did sound like I had a small backfire/misfire happening.

Thanks for any help

It sounds like you have a very typical problem with this car.

If you have already replaced the O2 sensor you probably are in the early stages of a clogged catalytic converter. There will be no odor just a clogged converter. You can get a generic very inexpensive replacement from any auto supply store.

The second reason but not as likely is that you have an exhaust leak that is confusing the O2 sensor from the reading it is expecting.

Remember that EPA components like cat converters, EGR valves, etc. have their own warranty of 80,000 miles and as high as 100,000 miles so it might be covered under warranty. You would still have to pay for the labor if you can't do it yourself.