Update: P0420 ---- first time i have ever heard of this

[AccordUser]

Okay, so for those who have not followed my posts on other P0420 threads. Here is a long story short.

Replaced (in order)
both o2 sensors
ALL SPARK PLUGS
throttle body gasket
EGR gasket
PCV valve and grommet
Lastly...Cat Converter (with a magnaflow)


cleaned (in order)
Throttle body
IM (gasket looked fine, didnt replace)
EGR (sprayed TB cleaner, not too much)



Check engine light came back on but goes on and off, but car runs fine.
The other day I cleaned my car, and took off the plastic engine covers and pulled the fuse to reset CEL. I drove my car the rest of the week (CEL usually would come on within 20-30 miles.) and the CEL did not come on. It hase now been 115 miles. So, I thought that was strange. Then i realized i forgot to put my engine covers on. the only one that i didnt take off, was the one that is on the front (near oil cap). all others were removed when i cleaned the car. anyway, i thought that maybe i had a vacuum leak, and my engine covers were trapping the fumes, and the vacuum leak would suck it up, causing the p0420. so at 115 miles, i put ONLY the middle cover on (goes in between the cylinders, by fuel rails). My light came on at 134 miles. WTF!!!! does this mean its a vacuum leak somewhere?

 

[soccerchamp16]

I have the same code but mine is throwing it for my exhaust so im tricking my o2 sensor into thinking its reading right thus clearing the code. As for you I don't know if you have a vacuum leak or not but thats what it seems to be looking like.

 

[AccordUser]

I have the same code but mine is throwing it for my exhaust so im tricking my o2 sensor into thinking its reading right thus clearing the code. As for you I don't know if you have a vacuum leak or not but thats what it seems to be looking like.

u must have an aftermarket exhaust?

 

[LeBirdNest]

P0420 is for catatylic converter operating below threashold. I think you putting on the engine cover was a coinsidence.

Edit: check out the "car threw a code" thread. You couldve just joined us in there.

 

[soccerchamp16]

u must have an aftermarket exhaust?

Yeah full custom exhaust, with a highflow cat to try to get rid of that code but it wont work until you trick it.

 

[001Stunna]

If this is really the first time you have heard of the p0420 code then that shows you have done/did absolutely no research on the code/issue. Nada. Nothing. Zilch. Zero. Because just typing p0420 on google brings up thousands of results, and many on here have had the issue numerous times.


Anyways p0420 means your ecu thinks your cat.converter is performing under its preset standard. this means that your converter could be performing at 90% but if the standard is 95% then the code will come up. meaning that the code does not mean your converter is fully dead and gone. it just means it is not performing up to what your ecu expects it to perform to. what reads/sends this signal to the ecu is your o2 sensor. if the o2 sensor is bad it could send a faulty code so the first step one should do is read live data through the o2 sensor.

What many have done to fix the issue is add a spark plug non fouler to move the o2 sensor a bit farther out of exhaust stream way, or replace your converter. even though most aftermarket converters will throw the code again in 2-3 years.

You wasted time/money in replacing your o2 sensors(even though changing them is not a bad thing), plugs, tb gasket, egr gasket, pcv valve and grommet. I'm pretty sure, as i mentioned above, you bought an aftermarket converter which are never packed with the same amount of precious metals as oem...hence do not work to oem standards after time passes.

The only ones i personally have had good luck with and so have others is magnaflow oem fit oem grade converters. If you go on magnaflows website and search for what fits your car you'll see what i'm talking about.

With all this said if you keep ruining converters then chances are the problem is not the converter but something with the engine itself. Coolant, oil, unburned fuel can all ruin a converter if they make their way to it.

 

[AccordUser]

If this is really the first time you have heard of the p0420 code then that shows you have done/did absolutely no research on the code/issue. Nada. Nothing. Zilch. Zero. Because just typing p0420 on google brings up thousands of results, and many on here have had the issue numerous times.


Anyways p0420 means your ecu thinks your cat.converter is performing under its preset standard. this means that your converter could be performing at 90% but if the standard is 95% then the code will come up. meaning that the code does not mean your converter is fully dead and gone. it just means it is not performing up to what your ecu expects it to perform to. what reads/sends this signal to the ecu is your o2 sensor. if the o2 sensor is bad it could send a faulty code so the first step one should do is read live data through the o2 sensor.

What many have done to fix the issue is add a spark plug non fouler to move the o2 sensor a bit farther out of exhaust stream way, or replace your converter. even though most aftermarket converters will throw the code again in 2-3 years.

You wasted time/money in replacing your o2 sensors(even though changing them is not a bad thing), plugs, tb gasket, egr gasket, pcv valve and grommet. I'm pretty sure, as i mentioned above, you bought an aftermarket converter which are never packed with the same amount of precious metals as oem...hence do not work to oem standards after time passes.

The only ones i personally have had good luck with and so have others is magnaflow oem fit oem grade converters. If you go on magnaflows website and search for what fits your car you'll see what i'm talking about.

With all this said if you keep ruining converters then chances are the problem is not the converter but something with the engine itself. Coolant, oil, unburned fuel can all ruin a converter if they make their way to it.

Preciate your opinion, but u should re-read my post, much slower than everyone else read it. i have heard of the p0420, i absolutely know what it is, and the recommended fix (cat replacement). I know its recommended a factory replacement. i know the stuff I changed prior to changing the cat converter were not all directly influential on the code. i have not replaced any of the parts i listed before (233,000 miles bro), and did them out of curiosity and preventative maintenance. i know about the magnaflow cat already, because thats what i replaced the bad cat with. the code goes away with the removal of the engine covers as stated prior, and comes back on when the engine covers are put back on the engine. i ALWAYS test my hypothesis before i post here to make sure im wasting nobodys time, and not blowing smoke, no pun intended.


moving on......i took it to honda, told them what happend, told them how i tested it, and the mechanic said good job, AND found the vacuum leak. that i had proposed. thanks for the positive feedback.

 

[soccerchamp16]

Uploaded with ImageShack.us

Heres the picture with what I did with mine. 2 spark plug defoulers attached to the O2 sensor to make it longer.

 

[bRaZEn_407]

Uploaded with ImageShack.us

Heres the picture with what I did with mine. 2 spark plug defilers attached to the O2 sensor to make it longer.

/thread

 

[soccerchamp16]

/thread

huh?