o2 sensor 'replaced' still CEL?
 

I got my o2 sensor "replaced" at a shop. It was throwing CEL for (cant remember the code off hand) for sensor 2 bank 2, and I get it back, and he says the code came up again because the battery died (I had a bad battery). Well I replaced the battery with a brand new one, and used my buddies scanner to clear the code, less than a day later, the code came back. My MPG has gone up (according to the little LCD screen) about 3mpg since it was in the shop, I don't know if my driving has changed, or what. Can anyone (TECH?) think of anything? Is this guy bull****ting me, or could there be something else wrong? I didn't pay for the parts/labor, the used car dealership I bought it from did, so...

Thanks guys!

RE: o2 sensor 'replaced' still CEL?
 

This is one of the most common mistakes, replacing an o2 sensor when you get a code saying their is a fault on a o2 sensor bank. The fault is just telling you that the o2 sensor is out of range. It could be the o2 is bad, but it could also be something else, such as a bad pre/catyltic converter.

RE: o2 sensor 'replaced' still CEL?
 

Thats why I always try to reccomend replacing both.
Each one being bad will throw a code for the other.
Make sure it is the same code as well.

RE: o2 sensor 'replaced' still CEL?
 

I'm 99% sure its the same code, unless there is multiples that will say Sensor 2 Bank 2? So you think that the pre-cat sensor on that side might be bad and trippig the post-cat?

RE: o2 sensor 'replaced' still CEL?
 

I can probobly find out by Tuesday what the exact code is, I have the old one (before it was fixed) written down, so when I get the car back from getting the TB service done, i'll plug it in again and check if they match

RE: o2 sensor 'replaced' still CEL?
 

OK let us know then.