Hi i´m driving a 05 cobalt ss stage 2 and is throwing this codes p1133, p0171 and p0420, the autozone guy said that changing the o2 sensor will fix this, on your experience what could help?

 

The p0420 is the rear o2 reading the cat isn't doing its job. The other codes are from the front o2, I threw those codes a while back replaced the front o2 and haven't seen them since. Replacing the rear wouldn't get rid of your code, you would have to replace the cat, put an o2 spacer or have it deleted through hp tuners.

 

Tnx, where can i get the o2sensor?? Checkers?? Dealership?? Online??