Switch back to regular octane gas and drive a few cycles to see if P0420 returns first.

 

My intermittent P0420 code seems to appear in the late fall/winter, and then go away again in the spring/summer.

I'm guessing that it's either the outside temperature, or more likely the formulation of the winterized gasoline (which is crap IMO ) that is causing it. I'm using 87-octane from Shell in mine.

There is a lot of reading on this topic here, search 'P0420'.

I'm living with mine for now. I don't have extra $$$ to throw at a converter either, and the reality is, the existing converter is doing just fine, Honda has set the parameter so tight that it doesn't take much for this code to be set. It's not anything close to a gross polluter like my '79 Chevy pickup, which even when perfectly tuned up will leave you gasping within in a couple of breaths!

 

the P0420 popped up once before while we were driving home from Florida and this was 6 to 8 months ago. at that time, I was using 89 octane.

it popped up once more in the last 2 to 3 months that is when I switched to 93 octane.

i've read and researched a lot on the topic and nobody seems to have a straight answer to a solution. its more like a hit and miss or trial and error solution....

in the last 2 weeks, while using 93, the code popped up and while I was getting ready to do the non fouler mod, the light just turned off yesterday.

 

It just means the converter has just about reached the limit of it's life. Honda doesn't set the standard as it is determined by the switching of the O2 sensers. Don't understand the logics. You have money to spend on 93 octane but not on a new converter? Replace the converter and go back to 87 octane gas and you will be money ahead. The standards are set by the EPA not Honda.

 

Don't understand the logics. You have money to spend on 93 octane but not on a new converter? Replace the converter and go back to 87 octane gas and you will be money ahead. The standards are set by the EPA not Honda.

The difference between filling up with 89 and 93 is a measly $2 - $2.50 per fill up. Now, if my math is correct....

$1000 / $ 2 = 500 fill ups which is also like saying 500 weeks...granting I fill up weekly which I do.

I hope you understand the logic here....

I don't have $1k to spend now, for me to be able to save $2 a week to go back to 89 or 87 octane. Even my local dealership can not assure me that the code will go away.

Like I said, the car runs fine and there is no single sign that the cat is bad. I would agree more with what redmondjp said than what you said....EPA set the standards, Honda made it too tight on setting the ECU though....

 

One item I have seen posted on various forums is the use of an anti-foul spark plug insert when having nuisance CEL converter codes. My understanding is that the anti-foul insert sets the sensor back slightly out of the main converter flow and may help keep the code from setting. Just a thought.

 

One item I have seen posted on various forums is the use of an anti-foul spark plug insert when having nuisance CEL converter codes. My understanding is that the anti-foul insert sets the sensor back slightly out of the main converter flow and may help keep the code from setting. Just a thought.

yeah, I was getting ready to do this when the CEL turned off out of the blue yesterday....

 

Like I said, the car runs fine and there is no single sign that the cat is bad.


The ONLY sign a converter is going bad ia the P0420 code. It doesn't affect the running of the engine or anything else. It only polutes the air. You aparently are in a location without mandatory polution tests.

 

The ONLY sign a converter is going bad ia the P0420 code. It doesn't affect the running of the engine or anything else. It only polutes the air. You aparently are in a location without mandatory polution tests.

you're conflicting with what you said here then...

http://www.odyclub.com/forums/showthread.php?s=&threadid=63342&highlight=P0420

"A code doesn't mean that component is bad. There could be underlying problems causing it. There are a lot of things to look a with a scanner to determine what the problem is."

if indeed my P0420 is cat converter problem caused, then why would the CEL turn on and off by itself? come to think of it now, it may be the O2 sensors after the cat that is bad or even just bad gas....

even when my city [I don't live in Memphis per se] does not require inspections, I believe I still could pass emissions test. there was a checklist to check the cat converter posted somewhere here and based on that, I DON'T see any signs of it going bad.

 

Not conflicting at all. A thorough check should be made but the end results with a continuing P0420 code and no other codes the result will be the same, the converter is marginal and about worn out. O2 sensers are monitored closely also and will through their own codes. You are probably referencing this article http://www.troublecodes.net/articles/catfailure/ which I have posted many times. A thorough understanding of the process and you will understand why the code goes on and off. It is an analog function and when the converter is magginal many environmental conditions can cause it to go on and off. There is enough history here to this problem with the converter. I graph my converter at least once a year to monitor it's demise.

 

Not conflicting at all. A thorough check should be made but the end results with a continuing P0420 code and no other codes the result will be the same, the converter is marginal and about worn out.

Ok...you make it sound like it's really the converter then. so if I replace it, and the code shows up again...what now? I'm out $1k and with a CEL....

 

You don't have inspections so why change it at all. Just get a code reader and check once in a while that it isn't a different problem. As I said a bad converter doen not affect anything else only polutes.

 

You don't have inspections so why change it at all. Just get a code reader and check once in a while that it isn't a different problem. As I said a bad converter doen not affect anything else only polutes.

My research indicates that even with the P0420 light on, the van passes the tailpipe emission (FTP) with flying colors. You can quote me on that. There are many many studies confirming that finding if you google it.

Essentially, the Honda parameters are more stringent than necessary.

- Vikas

 

My 1999 EX began exhibiting the P0420 converter light at 99,400 miles, in the fall of 2003. I was on vacation and had the code checked in case it was a transmission code. The dealer said the converter needed to be replaced, but it could wait until I got home, there would be no harm to the engine.

By the time I got home, the light had gone out. Over the next 2 years the code would appear an disappear, but was off at inspection time. The third and fourth years I was able to pull fuse 13 to reset the light, and pass inspection after driving 80 miles before the light came back on.

By July 2008, at 190,000 miles, the P0420 code stayed on all the time and I replaced the converter ($600. online at Majestic Honda + $70. labor at local muffler shop) to pass inspection. I have not seen the CEL on since then.

I currently have 233,000 miles on the van. still using the original oxygen sensors. My overall mileage has actually improved .5 mpg for the last year (20.5 - 21.0) and the van is running great.

 

Wow, $1000 ? ,

What we really need is someone who has a fancy OBD2 data logger to test a few vans or log a long term test where the code420 is being flagged periodically. To Compare the code throwing van with new converter or a van with the extension fouler would be priceless.

I have a feeling we would see only brief fluxuations in the oxygen sensor voltages which are enough to throw a code.
Corrosion on the sensor itself or a bad ground path are my thoughts. ( the spark plug fouler would provide new metal and a better connection....at least until the aluminum gets corroded by the salt of winter roads). I have not tried the fouler yet but I would still be interested in seeing a graph of before and after on what readings result.

If converter is faulty.....correct me if I am wrong but it should become more faulty as time progresses. I have been resetting the code upon random frequencies for the past two years and just a year after a cheap converter replacement. It seems to be more prevalant in the winter but seems to disappear completely upon occasion in summer (dry).

Sorry, I have nothing constructive to add (yet) only the same old questions.
If you think you need to get rid of the code use the anti-fouler method, let me know how long it works.

 

Is it really $1000 bucks to replace it? I just got the code my second time... First time it came on I went to Autozone and the guy reseted the light, after about 3 weeks it came back on with the same code. I'm about to purchase the part from http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&_rdc=1&item=320468563521 and have my mechanic put it on. He said he would charge me about 160 bux for labor

 

Computer compares the front and the rear sensor. If the rear sensor starts following the front sensor too closely i.e. if rear also switches quickly as the front, then computer knows converter is not doing its job.

Here is the rub; the threshold at which computer decides to throw the code, is set way too low. If the converter efficiency were to drop from 100% to 90%, the computer throws the code. However, your tailpipe emission as measured by FTP would have barely perceptible increase. In general, your van's emissions are less than tenth of the federal limit when it is running right. With the P0420 code constantly on, the increase in the emission would be still a noise in the measurement; it might at worse become ninth of the federal limit.

By the way, because of the way system is designed, bad sensor will NOT trigger P0420. A bad sensor does not switch fast. P0420 indicates fast switching sensor i.e. a working sensor.

If you really want to know everything about P0420, search under my name.

By the way, some manufacturers issued TSB and reprogrammed the computer to change the threshold i.e. Nissan did it on my 2000 Maxima. It does not work all the time as the code came back after a thousand mile and since I was within the 8/80K federal emission warranty, I got one converter from Nissan, gratis. Of course the other one went bad after another 30K but then it was no longer covered under warranty. Most vehicles will start giving P0420/P0430 at 70K-150K; some sooner some later.

- Vikas

P.S. Amazon sells some snake oil type converter cleaner. It is expensive but if you are going to spend $1000, why not try $30 solution and see if it really cleans the converter as claimed. The idea has merit and there are patented methods which are used to clean stationary catalytic converters although I am skeptical of it working on vehicles converter as the chemical has to survive the combustion process before it can land on the converter chamber. Please let us know if you choose that route.

 

I'm guessing for me my cat needs to be changed. I;m at 160,000Miles and I feel like when I'm taking off the car sort of struggles to pick up full speed till after. I'm not sure if it could be the O2 Sensor or the cat though and not sure which to purchase to have the mechanic put it on.

 

I might go check out cat converters when finances permit but the other day, I thought...why not buy one from a scrap or junk yard.

I called a few places and everybody told me that it is illegal to sell used cat converters all throughout the U.S.

The main reason they said was it was all tied to the emissions law.

Is this true?

 

I might go check out cat converters when finances permit but the other day, I thought...why not buy one from a scrap or junk yard.

I called a few places and everybody told me that it is illegal to sell used cat converters all throughout the U.S.

The main reason they said was it was all tied to the emissions law.

Is this true?

I wonder why they are so cheap on ebay? $126 shipped it says it also keeps the CEL light off

 

I wonder why they are so cheap on ebay? $126 shipped it says it also keeps the CEL light off

they are most likely not the OEM ones....

 

they are most likely not the OEM ones....

Would it make a big difference on performance? According to auction details it says it's direct OEM fit.

 

Would it make a big difference on performance? According to auction details it says it's direct OEM fit.

performance? no....code compliant, yes...as others have done, using non OEM units still throws the P0420 code...

direct OEM fit is like saying, it will install and run but its not a Honda product.....a very good marketing geek speak...

 

From what it says in the specs in the auction it says:

This is OEM replacement Catalytic Converter for all the above models
Unit features LARGE OBDII-Configured catalyst, specific for these engines,
and designed to keep the check engine light off ( most aftermarket units will not! )
409 stainless steel construction, heavy duty flanges, exact bolt spacing for easy installation
Quality construction, please compare this to other aftermarket units !!!
Ours has MUCH LARGER SUBSTRATE ( material inside ) AND HEAT SHIELD !!!!!
**** Meets or exceeds EPA requirements ****

The store is a power seller... But I'm wondering if it would give me problems passing inspections hrm.. I'm new to all this so sorry for any dumb replies/questions, I appreciate your input.

 

From what it says in the specs in the auction it says:

This is OEM replacement Catalytic Converter for all the above models
Unit features LARGE OBDII-Configured catalyst, specific for these engines,
and designed to keep the check engine light off ( most aftermarket units will not! )
409 stainless steel construction, heavy duty flanges, exact bolt spacing for easy installation
Quality construction, please compare this to other aftermarket units !!!
Ours has MUCH LARGER SUBSTRATE ( material inside ) AND HEAT SHIELD !!!!!
**** Meets or exceeds EPA requirements ****

The store is a power seller... But I'm wondering if it would give me problems passing inspections hrm.. I'm new to all this so sorry for any dumb replies/questions, I appreciate your input.

that's all marketing speak....

it's still not a Honda product...if I had the original one and sell it on ebay...I will only put one line. "Original Honda Catalytic Converter for 2001-04 Honda Odyssey p/n:-------"

and none of that marketing BS.....

it's just like the clone iPhones you see on craigslist...