P0420 - Catalytic Converter code - Replace Cat?

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Originally Posted By: The Critic
At your mileage you may just need a cat. But there is updated PCM software available to address a "false" P0420 on 06 and 07 Accords.
+2
 

CT8

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07 Honda Accord - 572k - Bulk oil/filter ??? This is BITOG the oil experts know no engine will live past 30.000 miles unless you run Amsoil and some trick oil filter changed daily
 
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If the cat gets plugged you will know it as you can't hardly get over 30 mph. If you monitor the second O2 voltage, when cruising it should average just under the first O2s peak voltage. Usually around 600-700 on my cars. If it is oscillating and following the front O2 voltage then the ct is not working.
 

ThirdeYe

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Just wanted to say thanks to everyone so far for the input. Its been very helpful and I appreciate it. I think what ill do is monitor the oil usage, if any, as well as the gas mileage and see how it goes. So far I do not notice any issues with a lack of power, so I do not believe it is plugged. P.s., yep it made it to 572k on bulk oil changes at the dealer every 8-10k
 
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Of course the P0420 triggered after replacing the O2 sensor! That test was deferred because of the faulty O2 sensor. Don't listen to morons who tell you to replace the secondary O2 sensor. They do not understand how P0420 is triggered or how O2 sensors fail as they age. Either put the space on the secondary sensor to fool the computer or replace the converter with the new OEM (equivalent) one. Anything else is chasing your tail.
 
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Originally Posted By: bdcardinal
Assuming you replaced the cat monitor sensor, you can always stack 2 spark plug non-foulers with the top one drilled to push the cat monitor out just enough to turn the light off. Not in the spirit of the game, but it usually works.
Works like a charm. I've done this several times.
 
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Walker has a rebate promo going on, $50 rebate on any cat. And they're a good price on Rock Auto, as well. It will end up costing under $100 after rebate smile
 
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In certain cases I've had luck getting P0420 and P0430 codes cleared by cleaning the MAF. I know it sounds unrelated but a dirty MAF will cause some funny codes.
 
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Originally Posted By: slacktide_bitog
Walker has a rebate promo going on, $50 rebate on any cat. And they're a good price on Rock Auto, as well. It will end up costing under $100 after rebate smile
Don't expect any money out of them. I sent in for a rebate; got a letter saying there's a problem, I called the 800 number, they acknowledged there wasn't a problem, and now I'm in limbo of "your rebate was approved; we'll mail a check within 72 hours". Since May. frown OP, I would keep on keeping on. Aftermarket cats aren't that great for emissions anyway-- they just barely work. Only fix the cat if you want the light off so it'll show a "real problem" when it comes on.
 
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Aftermarket cats don't have to last as long as the original cat. I think the federal standard is an 80k warranty on OEM and Pzev cars have to have 150k warranties. I believe the aftermarket ones are only 25k. I think they figure that by the time you need an aftermarket one, you probably won't be driving it anywhere as long as the original cat.
 

JTK

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Originally Posted By: Vikas
Of course the P0420 triggered after replacing the O2 sensor! That test was deferred because of the faulty O2 sensor. Don't listen to morons who tell you to replace the secondary O2 sensor. They do not understand how P0420 is triggered or how O2 sensors fail as they age. Either put the space on the secondary sensor to fool the computer or replace the converter with the new OEM (equivalent) one. Anything else is chasing your tail.
Seriously? LOL! Of course the original upstream O2 sensor and likely downstream are a bit sluggish due to the miles on them. If the "test was deferred" long enough, a CEL would be set. The delta between the two will change any time either one is swapped. As long as the proper O2 content drop is detected by the downstream, P0420 isn't an issue. Care to explain the vikas way this all works?
 
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The way the cats are checked by the post cat O2 is to see how much "storage capacity" the cat has. It will drive the mix lean then rich to see where the 2nd O2 runs. The post cat O2 should normally run near the high voltage of the primary O2 as it oscillates. As an example, if you see the primary O2 peak at .750vs, The second O2 should be near a steady .700+ voltage when cruising on the highway in closed loop. At idle this will drop to around .100v or even less.
 
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Since MI doesn't do much about CEL light. You can either replace it with an aftermarket CAT (so you don't have restriction just in case it is plugged), and / or put that spark plug non fouler thingy on the downstream O2 to make it "work". It really depends on whether it is plugged or not. At that mileage putting OEM cat on is a waste of money, aftermarket is good enough. Going 10w30 or 10w40 to slow the oil burn?
 
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Here is a layman's explanation:- The p0420 algorithm measures the cross counts [number of transitions of O2 sensor from high to low] of both the sensors and compares them. They need to be lot further apart. If the rear starts mirroring the front, computer knows catalytic converter is not doing its job. You want rapidly switching front and minimally switching rear. Older O2 sensors become lazy rather than becoming overactive. You should now be able to figure out why replacing the older (and possibly lazy) rear sensor is counterproductive to masking p0420 code. The principle behind the fouler is similar. You fool the rear sensor and make it NOT response eagerly. Do you now understand why putting a new sensor there is a retarded idea? On the other hand replacing the front one has merit.
 
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