2007 Honda Accord 2.4 w/P0420

[901Memphis]

Helping a Co worker with this issue. It's a 2007 Honda Accord 2.4 with the P0420 code. Car has 130k miles and recently a few weeks ago had random multiple misfire so I recommended oem plugs and ignition coils which he replaced and that code is now gone and hasn't come back.

Now this P0420 code pops up, should I just recommend him a good convertor and be done with it or is there a common cause on these cars I'm not aware of?

Rockauto has rear and center converters... Which one is typically the bad one? If so are there any brands to avoid with Honda converters.

 

[AKhan87]

I have had success with Walker universals, ebay or random no name brands are just awful because when it is REALLY COLD they give a P0420, which goes away once it isn't that cold anymore but no matter what, a good converter will not give you codes.

 

[The Critic]

It may not need a converter. Check TSB#12-052. There is a PCM software update available to change the methodology that the PCM uses to recognize a deteriorated converter.

 

[KingCake]

The misfire probably cooked the cats.

 

[slacktide_bitog]

Walker and Eastern direct-fit are the best

 

[901Memphis]

Originally Posted By: KingCake
The misfire probably cooked the cats.


It was only misfiring for about a week or so before he put the new parts in.

 

[The Critic]

Originally Posted By: 901Memphis
Originally Posted By: KingCake
The misfire probably cooked the cats.


It was only misfiring for about a week or so before he put the new parts in.


In that case I would definitely try the PCM update first. Anyone with a J2534 interface can perform the update. Honda is one of the few OEMs that does not charge for the software or firmware downloads.

 

[901Memphis]

Originally Posted By: The Critic
Originally Posted By: 901Memphis
Originally Posted By: KingCake
The misfire probably cooked the cats.


It was only misfiring for about a week or so before he put the new parts in.


In that case I would definitely try the PCM update first. Anyone with a J2534 interface can perform the update. Honda is one of the few OEMs that does not charge for the software or firmware downloads.


Thanks for the information, I will certainly recommend my Co worker seek out the TSB before throwing more parts at it.

 

[Bud_One]

Originally Posted By: The Critic
It may not need a converter. Check TSB#12-052. There is a PCM software update available to change the methodology that the PCM uses to recognize a deteriorated converter.


This...

 

[NormanBuntz]

This problem was just addressed by the surviving Magliozzi brother in the paper last week. He said if the code refers to a bad cat, it doesn't say which one is bad or both. He said replace the front cat first since it usually gets fouled first. Then retest and replace the second one only if needed.

 

[Vikas]

Most of those TSB just change the threshold at which ECM throws the code. Since it is free, you have to do that first before doing anything else. Incidentally, this is how manufacturer usually gets out of fixing the converter within the EPA mandated timeframe! When the converter does start going bad, the check engine will light even after the TSB but manufacturer hopes that it will happen AFTER the EPA mandated period!

 

[Trav]

Originally Posted By: 901Memphis
Originally Posted By: KingCake
The misfire probably cooked the cats.


It was only misfiring for about a week or so before he put the new parts in.


That's way more than enough to kill a cat. Never operate a cat equipped car with a misfire other than to get it short distance home or shop, even then disconnect the injector to the misfiring cyl if possible.

 

[901Memphis]

Originally Posted By: Trav
Originally Posted By: 901Memphis
Originally Posted By: KingCake
The misfire probably cooked the cats.


It was only misfiring for about a week or so before he put the new parts in.


That's way more than enough to kill a cat. Never operate a cat equipped car with a misfire other than to get it short distance home or shop, even then disconnect the injector to the misfiring cyl if possible.



Well he is going to get the update at the dealer i believe, and if that doesn't work he has no problem replacing the cat.

Should i recommend he replace the oxygen sensor too at the same time?

 

[Trav]

Its always a good idea to always replace the front O2/monitor when replacing a cat, don't worry about the rear.
The older and slower the rear the better as long as its working and not throwing a code.
If the Honda cat is huge money and he want to save a little $$ use a Walker cal cat (if available) or Eastern, the cal cat made for NY and other cal norm states will fit but its got a lot more wash coat and longer warranty.