Hi I just bought a 2000 ex n it just passed smog with flying colors the day I bought it..2 days later the check engine light came on.. P0420 came up so I was told to change the o2 bank 1 sensor..so I did but with a universal one.. Well needless to say the same code popped up.. Should I just get the more expensive kind our is there something else that's going on? My mechanic said it's not my cat n I have no exhaust leaks..can someone please help me?

 

have you try to change the 2nd o2, after/on the cat?

 

+1 the second sensor controls the P0420 code. If the smog test involved measuring pollutants at the tailpipe and it passed, cat would have been OK.

 

Yeah so the cat is ok just the #2 o2 sensor is bad...out looks brand new though..

 

Would that code effect my mpg?

 

Yes, it will affect the performance of you car, the 2nd O2 gives signal to control your fuel, either running lean or rich.. etc..