So my service engine light came on a few weeks back. Took the car to Autozone and it's throwing the P0420 code. From a brief forum search, I found that it can be the rear O2 sensor or the cat.

So here are my questions:

1) I have not noticed any loss of performance, but I have noticed the smell of exhaust in the cabin every time I put the pedal to the floor to have a little fun. Is this related to the code or cat?
2) If it's not the cat, what's the best approach to troubleshooting the sensor?

Thanks
J.D.

 

Is it the stock header or down pipe? This usually is a Problem with the cat. Usually seen with someone who is "catless" also I'm pretty sure the stock cat is 8yr 80,000 mile warranty.

 

I bought this vehicle used but I believe the headers and cat are stock. It does have a Borla exhaust but I'm almost certain that it's a cat back exhaust. Is the smell in the cabin a result of a faulty cat? Now that I think about it, when I bought the car I can remember the same smell. Just didn't think anything of it.

 

You might have an exhaust leak. Check all the bolts and clamps. If thats not it I would suspect the CAT.

 

Like a phosphorous smell or exhaust smell? Also, dealer will replace 02 sensors for 8 or 10 years, I got a letter from MINI USA regarding 02 sensors.