[Spdbump]

If failed some states the emissions warranty is longer than others. If you are in one of those states then dealer will replace for free or a small charge. See chart attached but make sure you pull the same information for your year. Mine is a 2013. Although with your time and mileage may not apply. I hope you have not been driving it with codes long enough to fall out of the warranty.

Do you have error codes? If you do make sure it is the CAT(S) (There are 2 of them) have failed. Many things other than the CAT(s) can cause errors.It can be an 02 sensor or other issues. You can do it yourself or have any shop replace it with one made for CR-Z(or even a universal), some states (CA) you cannot replace with used or one that is not CARB certified. Check your laws in your area. I will warn you they are expensive. Go look at RockAuto to get an idea.

There are lots of already existing threads on the Cats and the codes they can generate. I merged your thread in with one of them. Never just throw parts at a problem, you will spend a lot of money for no reason. Get codes, look up test and repair process for that code. Most expensive place to replace one (or both) is a dealer.

Many here have removed them and replaced with "test pipes" and used a tuner to turn off the codes. In many places the car will then fail visual inspection and or never be in ready for an inspection.

If you replace a bad cat(s)( or 02 sensor(s)) with good after you drive the car X Miles or or Y Starts the light will go off and car will go into ready when scanned.

 

[startrek]

I just order my downstream O2 sensor off rock auto and fingers crossed that'll fix it.

In case it doesn't has everyone just replaced the second cat?
I really don't want to replace the header cat. Seems like a pain to get in there

 

[Spdbump]

From reading here you can just remove the second CAT you only need the one between the 2 sensors.

 

[NY-Z]

Only the first cat is monitored, the second one is for further "cleanup" of the exhaust but not monitored with 02 sensors.

 

[startrek]

Only the first cat is monitored, the second one is for further "cleanup" of the exhaust but not monitored with 02 sensors.

For future P0420 code getters I have changed my downstream O2 sensor and will report back.
I am hoping this will solve the issue and not have to replace the cat

 

[rupps5]

I have been having the p0420 code pop up lately. Trying the spacer trick, hoping it works. 215,000mi 2011

 

[Spdbump]

With your mileage, you should replace the sensor(s), they do wear out and get contaminated.

I have been having the p0420 code pop up lately. Trying the spacer trick, hoping it works. 215,000mi 2011

 

[Koala Yummies]

Yeah at that mileage the sensor is probably dead (though if you have a scan tool you can test it).

But also with that mileage prepare for the possibility of needing a new cat. Contrary to popular belief and many a mechanic myth they do wear out even absent PGMFI issues.

But I would swap the sensor first, the $59 Denso one at Rock Auto is basically OEM.

 

[Gambolt]

Guess i will tag onto this thread, I've been getting the code intermittently over the past year. I reset the code and wont see it again for a couple months. Lately, its been once a week or so. usually when i am in 6th gear and going slow. when i look on the scanner the sensor seems to be reading. since it is intermittent, I don't think I am going to see anything. Ideas? or just try a sensor? that's the downstream one on the link from above? BTW still at 335K highway miles

 

[Spdbump]

Guess i will tag onto this thread, I've been getting the code intermittently over the past year. I reset the code and wont see it again for a couple months. Lately, its been once a week or so. usually when i am in 6th gear and going slow. when i look on the scanner the sensor seems to be reading. since it is intermittent, I don't think I am going to see anything. Ideas? or just try a sensor? that's the downstream one on the link from above? BTW still at 335K highway miles

IMO at that mileage I would expect either the sensor or the CAT but sensor would be my first choice since intermittent.