O2 sensors and bad gas mileage

I get horrible gas mileage on my 98 4x4 and had a check engine light. I read that bad o2 sensors were the likely culprit, so I had them replaced. Not more than three weeks later, the check engine light is on again and my mileage is still bad (around 200 miles per tank). What would cause the sensors to go bad?

 

what code did you have.

 

More than likely if the fule milage is that bad it is not an o2. It's your a/f sensor. I know when mine went out I dropped down to 6mph.

Did you replace an o2? Old age will take them out most the time. Also if you get an o2 or a/f sensor use the denso. They work the best and last!


Blue

 

^^^what @nj636 asked^^^

What was your original code when your first CEL came on? Then what was the code when your 2nd CEL came on after you replaced your O2 sensor??

Also...for thoes 3 weeks, did you get your "normal" gas mileage once you changed the O2 sensor? If so...once your CEL came back on...did you again go back to bad gas mileage?

- Russel