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#2455048 - 12/06/11 05:26 PM 2006 Accord, 4 cylinder code P0420
greenjp Offline


Registered: 05/19/04
Posts: 1213
Loc: Germantown, MD
The wife's 2006 Accord with about 55k miles on it just turned up code P0420 today, catalyst efficiency below threshold (bank 1). A little research indicates this probably means either the post-cat oxygen sensor is bad, or the sensor is fine and the cat itself is actually going bad. Any thoughts on those, how to check, etc?

Also, am I correct in believing this ought to be covered by the mandated extra warranty on the emissions control system? Thanks,

jeff

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#2455056 - 12/06/11 05:31 PM Re: 2006 Accord, 4 cylinder code P0420 [Re: greenjp]
JRed Offline


Registered: 06/01/09
Posts: 1688
Loc: Virginia
Might be covered by emissions warranty, might not.

Probably a bad O2 sensor unless your engine has other fairly obvious problems.
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#2455057 - 12/06/11 05:31 PM Re: 2006 Accord, 4 cylinder code P0420 [Re: greenjp]
HTSS_TR Offline


Registered: 04/17/06
Posts: 19528
Loc: Lake Forest, CA
Emission system is covered with 10 years 100k miles warranty.
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#2455078 - 12/06/11 05:43 PM Re: 2006 Accord, 4 cylinder code P0420 [Re: greenjp]
Bill in Utah Offline



Registered: 11/11/02
Posts: 12829
Loc: UT
2006 is it not 8 years or 80,000 miles unless you live in one of the "other" states like CA, NY, NJ and such? And those states depends on if its a PZEV and such rated vehicle.

I'm pretty sure 8 years or 80k. Take it to the dealership and let them figure it out since you are under either number.

Pretty early to see the emission codes popping up...

Bill

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#2455090 - 12/06/11 05:55 PM Re: 2006 Accord, 4 cylinder code P0420 [Re: greenjp]
Trav Offline


Registered: 11/20/06
Posts: 14347
Loc: MA, Mittelfranken.de
Don't do or change anything, you could end up on the hook for the repair. As Bill said go to the dealer and let them worry about it.
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#2455117 - 12/06/11 06:23 PM Re: 2006 Accord, 4 cylinder code P0420 [Re: greenjp]
beast3300 Offline


Registered: 12/24/09
Posts: 3131
Loc: Ohio
I thought it was 8/80, go to dealer.
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#2455195 - 12/06/11 07:31 PM Re: 2006 Accord, 4 cylinder code P0420 [Re: greenjp]
Tegger Offline


Registered: 03/20/06
Posts: 2061
Loc: Canada
Originally Posted By: greenjp
The wife's 2006 Accord with about 55k miles on it just turned up code P0420 today, catalyst efficiency below threshold (bank 1). A little research indicates this probably means either the post-cat oxygen sensor is bad, or the sensor is fine and the cat itself is actually going bad. Any thoughts on those, how to check, etc?

Also, am I correct in believing this ought to be covered by the mandated extra warranty on the emissions control system?

You are correct. The federal EPA warranty is 8 years or 80,000 miles, whichever comes first. That's a ONE-TIME ONLY warranty, so subsequent cats are subject only to the maker's own warranty. This is explained in detail on the EPA's website.

It's not the downstream oxygen sensor, so forget about that idea. Unless there's an exceptional issue, the cat is simply bad.

You MUST insist the dealer check for TSBs for your vehicle and P0420 DTCs. They are unlikely to check on their own, and you'd be surprised what can lead to a P0420 that originally had nothing to do with the cat. I have a page on my site where I compiled a list of TSBs outlining problems that led to cat damage, and needed to be corrected before the cat was replaced. See at the bottom of this page:
http://www.tegger.com/hondafaq/p0420/index.html

If you've been careless enough to allow the car to run out of gas once or twice, or to have driven for extended distances with a very low fuel-level, don't tell the dealer. That is considered abuse, since it causes substantial damage to the cat, and it may complicate the warranty claim. There are warnings about such behavior in your Owner's Manual.

Finally, DO NOT HAVE AN AFTERMARKET CAT INSTALLED, and DO NOT allow an independent shop to work on the car for this issue. Those would be the WORST things you could do right now!



Edited by Tegger (12/06/11 07:33 PM)
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#2455237 - 12/06/11 07:58 PM Re: 2006 Accord, 4 cylinder code P0420 [Re: greenjp]
artificialist Online   content


Registered: 09/23/07
Posts: 8257
Loc: Florida
Go to the dealer and be quick about it.

When a cat located near the cylinder head fails, sometimes it gets sucked back through the exhaust valve and abrades the piston rings and bores to death. This frequently happens to 2.5L Nissan engines.
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#2455397 - 12/06/11 11:11 PM Re: 2006 Accord, 4 cylinder code P0420 [Re: greenjp]
L_Sludger Offline


Registered: 10/04/09
Posts: 2675
Loc: NORTHCOM AOR
Go to dealer OR install two spark plug anti-foulers in series into the O2 sensor bung after the catcon and then screw the o2 sensor into there. that'll take care of the p0420 code

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#2455506 - 12/07/11 06:52 AM Re: 2006 Accord, 4 cylinder code P0420 [Re: Tegger]
greenjp Offline


Registered: 05/19/04
Posts: 1213
Loc: Germantown, MD
Great info everybody (tegger especially), thanks a lot. There is one service bulletin for this type of car, relates to an ECM problem where it incorrectly interprets sensor inputs and throws this code. It's listed for the '03 4 cylinder Accord so it may apply. Either way it sounds like I ought to get it to the dealer.

jeff

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#2455884 - 12/07/11 02:39 PM Re: 2006 Accord, 4 cylinder code P0420 [Re: greenjp]
Vikas Offline


Registered: 07/22/05
Posts: 10605
Loc: NorthEast
The TSB most likely relaxes the ECM criterion to throw the code. However, if the cat has really died, the code will come up again, hopefully before 8/80K is up.

Forget about the anti-fouler for this vehicle; this is a manufacturing defect and it will be corrected by the manufacturer.

- Vikas

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#2462069 - 12/14/11 07:17 AM Re: 2006 Accord, 4 cylinder code P0420 [Re: Vikas]
greenjp Offline


Registered: 05/19/04
Posts: 1213
Loc: Germantown, MD
Minor update - the CEL went out yesterday. The code is still stored but no light. No pending codes either which is different from before.

A week ago I reset it and it came back on pretty quickly, so I'm curious to see what happens next. Still planning to take it in to get looked at in a couple days.

I noted that something similar happened a few years ago on my 2003 Saab. Got P0420, cleared the code, and it never came back. That car is at 157k miles and every piece of the exhaust is original.

jeff

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#2462648 - 12/14/11 05:06 PM Re: 2006 Accord, 4 cylinder code P0420 [Re: greenjp]
Vikas Offline


Registered: 07/22/05
Posts: 10605
Loc: NorthEast
If yours is under 8/80, why did you reset the code?

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#2463101 - 12/15/11 06:15 AM Re: 2006 Accord, 4 cylinder code P0420 [Re: Vikas]
greenjp Offline


Registered: 05/19/04
Posts: 1213
Loc: Germantown, MD
I know from past experience that many codes will simply never come back, indicating that there was a non-existent or very marginal problem. So that's usually my first trouble shooting step. Like I said, on my Saab this very code appeared once, I cleared it and it never returned. That was almost 3 years and 50k miles ago.

With this occurence on the Accord, it came back very soon after clearing it. Stayed on for about a week then the CEL turned off by itself. I checked and the code remains stored.

jeff

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#2463329 - 12/15/11 12:02 PM Re: 2006 Accord, 4 cylinder code P0420 [Re: greenjp]
Vikas Offline


Registered: 07/22/05
Posts: 10605
Loc: NorthEast
If you get past the warranty period, this repair will cost you four figures. I understand your concern about visiting dealer but in this particular case, it is warranted (sorry for the pun).

I really wish somebody had put some sense in to me when my Honda was doing similar things. By the time I realized about federal emission warranty of 8/80K, the van had already crossed that mileage. I used to reset the code but it used to randomly pop back. It first started when the van had under 60K miles.

You have to take my word but when it comes to P0420/P0430, you are not going to find anybody who is more knowledgeable than me :-) OK, I am half kidding!

- Vikas


Edited by Vikas (12/15/11 12:03 PM)

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