Getting the P0420 code

[DrVolkl]

So should I replace the O2 sensors first and cross my fingers? I can't believe the cats would be going on a 2008 car.

My car does have headers... I'm hoping a sensor got dinged when the previous owner swapped back the stock exhaust.

Anyone else ever deal with this?

Car seems to run fine... but then again. I've only owned it for a few months, so I really wouldn't know the difference if it was subtle.

[donoman]

Reset the codes and see if it fails again!

[DrVolkl]

Originally Posted by donoman

Reset the codes and see if it fails again!

Yeah, I did... it's been coming on/off for a month. When I checked the code it had logged it 4 times.

I reset it monday... still off today. Who knows... it's probably an o2 sensor failing but I'd hate to find out its the cats.

[donoman]

You can drive the car and when you turn it off, go take a whiff of the tail pipe. If you smell rotten eggs coming out of there, you've got a bad cat. It's not likely though, cuz your car is so new. I would guess it's just an O2 sensor.

Figuring out which O2 sensor is the next thing to do. I believe there is a pre- and post-cat sensor. If I were you and the sensors are different, I would buy the cheaper one (or easier one to get to) and swap it out. Of course, this assumes that you are doing the work yourself.