[PeterPerkins]

O2 sensors and CATS have a finite life and are expensive consumable items.

The P0420 code is flagged/signaled by the post CAT O2 sensor. So we have a few possible scenarios.

1) The pre CAT primary O2 sensor or wiring is bad/old, causing fluctuations being detected by the post cat sensor.
(This may also cause lumpy running or other fairly obvious issues/codes)

2) The post CAT sensor or wiring is bad/old, erroneously flagging up a bad CAT problem.
(Again this may also cause other codes, but not always.)

3) The CAT is actually bad/blocked and the code is correct.

In the past on the Insight I have used post cat O2 sensor spacers to move the secondary sensor slightly out of the gas flow which smoothes out fluctuations.
(It's a handy workaround for scenario 3 and possibly 2 if the sensor is just old) Cleaning/replacing the CAT etc are of course also options for scenario 3.

Attached is the advanced diagnostic P0420 pdf.
Although it doesn't help that much it's interesting reading.

 

[njbob]

Hi I have a 2013 CRZ with 235K. This car has been grea,t up until now I have 0 issues Getting 43 MPG. I had the CEL come on the other day took it to the Honda dealer. They told me it needs a new catalytic converter at a cost of $3200. I love the car but with that many miles on it I'd hate to do it then have something else happen. Or if it really the cat and not another issue, next step is to take it across the street to an independent mechanic, I have not pulled any codes from it. I see there are aftermarket cats out there at a reasonable cost. Anyone have any experience with these?

 

[Spdbump]

Pull codes and then follow diagnostics that codes indicate. If cat(s) consider trying one of the cleaning solutions but with that kind of mileage it is not to be unexpected that a cat will fail. You can order a universal cat from Rock Auto or used from https://www.redlineautoparts.com/honda-cr-z/ or some members have removed theirs and you might be able to buy one.

 

[njbob]

Thank you very much, I figure with that kind of mileage I would not doubt its bad. Going to see how much an aftermarket one is.

 

[Spdbump]

I still recommend pulling codes and having diagnostics done even after market Cats are $$$$$$$. Many have gotten away with 02 sensor replacement

 

[njbob]

P0420, I took it to an independent mechanic that will check out the o2 sensors.
In the past this guy has been reluctant to change parts unless he knows they are bad.

 

[Spdbump]

Per this it is the Cat but still could be the sensor. Your mechanic should know how to do the full testing process.

P0420 Honda: Code Meaning, Causes, Symptoms, & Tech Notes (With Video)

The Engine Control Module (ECM) monitors the switching frequency ratio of heated oxygen sensors 1 (front O2 sensor) and heated oxygen sensors 2 (rear O2

www.engine-codes.com

Here is summary:
As the code description implies the P0420 code means that the vehicle's control module has detected that the three-way catalytic converter is not working properly (is not as efficient as the factory is expecting). Replacing the oxygen (O2) sensors may sometimes fix the code, but in most cases, the catalytic convert needs to be replaced to fix the problem. If the P0420 code is combined with other codes, try fixing the other codes first.

P0420, I took it to an independent mechanic that will check out the o2 sensors.
In the past this guy has been reluctant to change parts unless he knows they are bad.

 

[MrFastFox666]

I see that places like Autozone have universal cats for $80-90. Not sure how well they work, but if it is indeed the cat, this is the route I'd go if I were in your shoes. at 235k miles spending big money on a cat doesn't seem worth it to me. Also pretty crazy to hear that a 'Z has 235k on the clock. Out of curiosity, have you owned the car since new?

 

[njbob]

Thanks all, I took it to an independent mechanic, they said the 02 sensors were ok and it is indeed the cat.
The cost to replace was $1200 Vs $3200 from the dealer.
I had them do the work and so far so good.
I am getting up there in age and being winter I do not have the where withal to lay under a car on a gravel driveway.
The cat was one that bolted right in no cutting out the old one.
I have owned the car since new with absolutely 0 issues other than regular maintenance.
I change the oil every 8K does not burn a drop.
I figured the car don't owe me anything so I went for it. Thanks

 

[Spdbump]

I am glad you got it fixed. I used to have a mechanic where i could order parts and they would install for me for only the cost of labor. On my previous car they replaced the full cat back exhaust and the full suspension including a strut tower bar and brakes.

RockAuto had this listed but not sure which would have been appropriate and this listing is for a 2013.

2013 HONDA CR-Z 1.5L L4 ELECTRIC Catalytic Converter | RockAuto

RockAuto ships auto parts and body parts from over 300 manufacturers to customers' doors worldwide, all at warehouse prices. Easy to use parts catalog.

www.rockauto.com

BOSAL / BRE 0963917 Premium Load OBDII; EPA / Federal Compliant Info One of our most popular parts $345.79

BOSAL / BRE 0962008 Manifold Converter; Premium Load OBDII; EPA / Federal Compliant Info $407.79

Just glad it is taken care of and will probably never need to be done again.

You change every 8K and ignore the minder? At least it is not every 3K. As I have stated before mine is by minder or once a year. The next one will be once a year.

Thanks all, I took it to an independent mechanic, they said the 02 sensors were ok and it is indeed the cat.
The cost to replace was $1200 Vs $3200 from the dealer.
I had them do the work and so far so good.
I am getting up there in age and being winter I do not have the where withal to lay under a car on a gravel driveway.
The cat was one that bolted right in no cutting out the old one.
I have owned the car since new with absolutely 0 issues other than regular maintenance.
I change the oil every 8K does not burn a drop.
I figured the car don't owe me anything so I went for it. Thanks

 

[njbob]

I do not ignore the minder, it is usually around 40% I use the semi synthetic not full.
I seen the one on Rock Auto I know the guy made a pretty Penney but compared to 3200 from the dealer I am happy.

 

[Spdbump]

You can wait a little longer for the oil changes semi synthetic is what the dealers use unless you specify full synthetic . There is no 100% conventional oil that is 0W20.

 

[Koala Yummies]

Reviving from 2 months to add some new notes and observation/opinion on P0420 CR-Z experience especially since a lot of these cars are getting up there in mileage. First off on this car its kind of a bs code. Due to auto-stop the cats can dip below ideal operating temperature and depending on the driving being done; short trips, long red lights, sitting in drive-throughs etc. they can potentially be in and out of temperature regularly which will affect their ability to perform as they should and thus trip erroneous (BS) codes temporarily. Its not necessarily bad! The sensors just saying 'hey, smells funny right now'.

My advice is to never panic if you get a P0420. Pull the CEL/MIL code at an autozone, your mechanic or whatever scanner tool you have and then clear the code and keep driving. (If you "hard-clear" the code by disconnecting 12V battery it will take some time to return to full OBD system ready)

It may come back. I've had this code hit dozens of times as the original owner of a bone stock very well maintained 2011 M/T. Replaced the 02 sensor a couple of times. A few times the code has even cleared itself with no intervention, no clearing the code myself. One time the code appeared, I did a number of hard accelerations on freeway onramps to get everything super hot and it went away by itself all on the same drive.

So never jump to the conclusion that it must be the cat. As I said I've replaced the 02 sensors a bunch of times and the code stays away for about a year. Probably wasn't even the sensor. So clear the code and keep driving. If however you get it repeatedly and very quickly after each clear then at least you have more solid evidence before you drop ~$400-600 on these expensive ass parts. And don't buy the Honda OEM one, screw them and that price. Let them sit there in their warehouses forever. And if the bourgeois California Air Research Board wants the poor plebeian proletariat peasants like us to be compliant then they should try helping out; no one can afford this crap.

Currently at 17x,xxx miles and had it pop up again recently. Thinking of running it over with a bulldozer. That should stop the code forever.

Also had the super duper fun pleasure of dealing with P0141 secondary 02 heater circuit malfunction which after diagnosing the entire electrical system turns out the circuit inside the ECM (ECU) had gone bad and needed to replace the fing computer. Super fun that crap was.

Hope everyone's been well. Its great to see so many of the regulars still here and helping out.

 

[njbob]

Very informative I never thought of that affecting the cat but I can see how it does. It never came on before for me and since I replaced the Cat I have driven it for several thousand miles and the code has not come back. I am up to 240K now. Intending on retiring soon so I will not need the real good mileage, but I think I may just run it till it dies. Glad I don't live in California, those regulations are excessive. And your right about Honda that was like telling me just go buy a new car.

 

[poognasty]

So I had a p0420 code pop up, I cleared it and then it always comes back. I got new o2sensors for the upstream and down stream, 8 weeks go by and it comes back. I got a catalytic converter but I guess I got the one with the resonator and not the part I needed which is the manifold.. has anyone else run into this problem?


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[Spdbump]

I just combined all of the threads for that code into this one thread for your education. In the future before posting please see if a related thread already exists. Generally if you have that code you have to replace the correct catalytic converter if using Cat cleaner and replacing O2 sensors does not work. If in CA you cannot install a used Cat and new ones due to CARB Laws are very expensive. Other places you can buy a used one or after market ( many members here have removed them and tuned out the code so they will sell it) but depending on inspection in your area it will not pass on visual inspection.

This has been discussed many times as you see above. Also see @HondaHolly's thread on this issue in her build thread.

I do not believe it is the manifold or the one with the resonator we have 2 cats you need the one between the 2 O2 sensors. One of the other members that has had this issue would know for sure. The Speed Bump has not had this issue yet.

So I had a p0420 code pop up, I cleared it and then it always comes back. I got new o2sensors for the upstream and down stream, 8 weeks go by and it comes back. I got a catalytic converter but I guess I got the one with the resonator and not the part I needed which is the manifold.. has anyone else run into this problem?


Sent from my iPhone using Tapatalk

 

[poognasty]

I just combined all of the threads for that code into this one thread for your education. In the future before posting please see if a related thread already exists. Generally if you have that code you have to replace the correct catalytic converter if using Cat cleaner and replacing O2 sensors does not work. If in CA you cannot install a used Cat and new ones due to CARB Laws are very expensive. Other places you can buy a used one or after market ( many members here have removed them and tuned out the code so they will sell it) but depending on inspection in your area it will not pass on visual inspection.

This has been discussed many times as you see above. Also see @HondaHolly's thread on this issue in her build thread.

I do not believe it is the manifold or the one with the resonator we have 2 cats you need the one between the 2 O2 sensors. One of the other members that has had this issue would know for sure. The Speed Bump has not had this issue yet.

———————
Thank you! Yeah I replaced the o2 sensors downstream and upstream. I also had my friend, who’s a tech at work, check for any leaks in and around the engine, which we didn’t find any. The car doesn’t misfire and it doesn’t seem to be lagging. But when I replaced the sensors, the light was off for 8 weeks and then came back on.. but I’m not sure which one the in between is, because I thought the one that has the resonator bolts in to the bottom of the one that has the manifold


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[Spdbump]

One of the members that has replaced the correct Cat will need to assist you. 2 are mentioned on Rock Auto and I am not sure which one is the right one. I would ask your buddy to help you identify the correct one that is the problem so you can buy just the one that needs to be replaced.

 

[psomero]

Way late to the game here, but came across this thread while trying to remember the price of the OEM cats while telling a story about what happened to my 2011 CRZ.

Car was in a wreck, got totaled out by ins co, just a resettable crash sensor code in DTC's and I cleared it out with a $189 Autel OBDII. Had to get a salvage title, which in California you have to smog the vehicle even if you're transferring the new title to yourself and even if it's currently not due for smog. Problem was I had a emissions code that had been throwing for ages that I never bothered to deal with. It was bad O2 sensor or bad cat per the guy at the local smog station. Clearing the code and then going to smog didn't work because in CA, they check DTC's and the code will be cleared but there is a counter which will not have accumulated enough data to pass test - auto fail. "Go drive 100 miles and come back"

Well, I knew I wasn't going to pass. In CA, it is illegal to use an aftermarket catalytic converter unless it is certified by the manufacturer through CARB (state air resources board) to pass emissions. Given the CRZ is a niche vehicle, there are no aftermarket CARB-certified cats. Period.

Tech suggested I look into the warranty on the OE units. I was at ~89k, so out of factory warranty, but the state had a 100k warranty that stacks on top of that. I was like uggghhhh, but he insisted I call the dealer. Dealer wound up replacing parts, no cost to me, and I even shamed them into driving it around enough to set the counter in the DTC's so it was a guaranteed pass on retest. I spent 3 hours a day in the car commuting at that point, so if I had to pick it up, fail again and go back, it would have been a huge hassle. They fixed it and it saved me thousands. I was honestly going to scrap the car if it wouldn't pass, given it was a salvage title and the CVT is going south anyways. In the past year, I haven't driven much and I sure am glad I'm not making payments on a new car I'm not driving.

TLDR; YOUR STATE MAY HAVE A WARRANTY THAT OVERRIDES THE FACTORY WARRANTY ON THE EMISSIONS EQUIPMENT. I GOT A FREE PAIR OF CATS BECAUSE CALIFORNIA HAD THAT. OP SHOULD HAVE LISTENED TO THE PEOPLE WHO STATED THAT ABOVE BECAUSE THEY WERE RIGHT. WHEN IN DOUBT, CONSULT A DEALER AND THEY WILL REPLACE YOUR BAD CATS FOR FREE IF THERE IS A STATE-MANDATED WARRANTY PERIOD STILL IN EFFECT.

 

[Israel Del real]

Does anyone know if I can change the catalytic converter on my CRZ myself or do I have to pay the dealer to avoid faults with the computer?
And which catalytic converter do you recommend?

My CRZ is about to hit 200k miles :,)