I know this should be in the lancer section but you guys know as well as i do no where near as many people look there as here....

I drive a 03 OZ rally. I purchased and installed a Greddy ti-C cat back approximately 4 months ago. About a month ago my CEL came on. I figured it was a bad o2 sensor and it was. However my mechanic told me that the code was for the o2 sensor and that was what was turning the CEL on but there was nothing actually wrong with the sensor it's self. He thinks it is the back pressure of the catback now that it has been covered in carbon. He said i could replace the o2 sensors to fix the problem so i could pass inspection but more likely then not the CEL problem would just come back. Has anyone encountered this problem before or know a way to fix this permanently with out replacing my cat back?

Thanks

 

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is this the pre-cat sensor or after the cat? have you or you mechanic actually seen the o2 sensor and saw the carbon build up? if it is the one after the cat, you may possibly have a faulty cat. the most probably cause is that the o2 sensor failed just randomly after you installed the exhaust. the car is 6 years old, o2 sensors do go bad on there own. i say just replace the sensor and you probably wont have the problem again

 

he was telling me that the o2 sensors are working correctly and that he cleaned them but when i left like 10 mins later, after i left,the light came back on .... do you think he is wrong and the o2 is actually broken ? cause i was going to replace them but he seems tot think that replacing them will only be a like putting a bandaide on the problem and it will come back.

 

I would try this first for the rear sensor:

https://www.evolutionm.net/forums/ev...ouler-how.html

If it won't fix the o2 cell then your sensors are bad.