92hondaex4door

i have an advanced auto cat on my GF's accord for about a year now. cel went off and has not come back on

DCFIVER

No you cant.

squallpro

I have a. 1999 honda accord lx. It has abt 170k on it and for the past three years I've had to change the cat converter. Cel keeps coming on about a month after I change my cat. I've changed all my o2 sensors and I know its not that but when I go to autozone or a mechanic they tell me its the cat and I know the cats bad and all but what's causing it to go bad so quickly?

phootbag

Catalytic converters fail in two ways; Surface contamination or physical degredation.

The causes of these types of failures can differ. Surface contamination can come in the form of a blown head gasket depositing coolant on the surface of the cat. Burning oil can cause soot to deposit on the surface of the cat. Running excessively rich can cause surface deposits on the cat which can cause it to fail. Basically, anything that coats the cat and prevents the exhaust gases from coming in contact with the surface can render the cat useless. I'm sure there is a way to "clean" a cat and cause it to function again without having to buy a new one.

Physical degredation is much more rare and can be caused by extreme overheating such as from lean misfires or from fuel burning inside the cat.

h0p3l355dork

3 cats in two years?! This tells me you're probably using aftermarket cat's.. or you are effing rich and can afford 500 dollar OEM cats. I had this issue in the past and toyed around with the defouler trick but decided to just bite the bullet and replace it with a new OEM cat from Majestic Honda. After 600 dollars parts and labor no more CEL and passed smog. To everyone that has the P0420 code, please just do yourself a favor in the long run and get the OEM cat. Sure an aftermarket is cheaper in the short run 150 vs. 500 but if you think long run that's 500 dollars for a cat that's guaranteed to last upwards of 8-10 years where as the $100- 150 aftermarket cat will last only 2-3 years. If you do that math (and plan to keep your car for a while), it will save you money in the long run.

phootbag

Exactly. Cheap is expensive.

DCFIVER

This exactly the reason that most aftermarket cats are no longer legal for sale on OBD 2 cars in CA. There are manufactured with only enough catalyst material to last a couple of years(reason why they are so much cheaper) The aftermarket cats that are available for sale now are required to have a minimum 5 year warranty.

Fastguy

Has anyone actually cleaned a cat? My head gasket went, car started using coolant. I fixed it , but now I am getting a PO420 code.
The car has about 183,000 miles on the original cat so it's probably going to need one anyway, just hate to replace such an expensive part on a 12 year old car.

trout63

I have the same code on a 99 Accord. Can someone tell me how to test the 02 sensor. Is there just one or are there two? Thanks

Hidenplanvew

snap on scanner or something that can read the sensor signal.. It should bounce from lean to rich and lean to rich your 2nd 02 will bounce alittle but should be pretty much flat

vick909

i would just change the o2 sensor first and drive the drice cycle to see the the light turns back on.

DCFIVER

Coolant absolutely destroys cats. Very common for a cat failure to occur after an HG failure...

chellscivic

Has your map sensor code popped up yet? I had the same symptoms and the timing belt was off by a few teeth.

Westeros01

Having the same code for my Honda Accord 2001. I experience noticeable loss of power when driving especially above 1500rpm and slight jerking which is also evident from the way the rpm clock needle rises above this rpm range. Instead of rising steadily and smoothly, it kinda stalls or rises haphazardly. But the car idles smoothly. Is anyone having thesame experience?

gmatknox

Integra_Boi;14106134.....or whatever......I got that code and see someone said the cat is clogged so replace....well....mine (1998 Accord V6) is running great....so....I don't think they run well with a clogged converter

MAD_MIKE

P0420 is simply "Catalyst system efficiency below threshold"
It just means the catalyst is unable to properly catalyze. That can happen from the engine in a bad tune from worn plugs, maladjusted valves, or clogged EGR. Check your engines running condition. Just because a code is not stored, does not mean there isn't a running issue.
With Hondas I've noted P0420 will pop up before EGR or a misfire code.

mf-doom

P0420 means the cat went bad.
If the egr went bad or the o2 sensors went bad they would give u that code. You get something like p0171 for engine lean. There is nothing else to look at with a p0420 it's always the cat.

GhostAccord

It is not always the cat.

I'm with MAD_MIKE on this one.

I have personally seen more than my fair share of P0420 codes that ended up being fuel related, not cat related.... Not saying that it's not your cat. But it is not always the cat.

You can google Honda Accord P0420 if you want, or go to CB7Tuner and look at the nice P0420 write up if you have your doubts!

MAD_MIKE

Nope.

DCFIVER

This true around %80-%90 of the time, but not always.
The vehicle absolutely has to be in fuel control in order for the cat to function properly. It is possible to run lean or rich enough to cause a problem with the cat oxidation but not set a lean or rich code. Most vehicles only code at around + or - %25 long term trim.
However once you get into the %15 range, gas mileage and catalyst efficiency will suffer.

MAD_MIKE

Not just Hondas, when the P0420 has popped up on other vehicles I've encountered non-catalyst deficiency issues are the problem.

From simple stupid issues like a loose spark plug, to neglect (valves need adjustment), or simply the PCM(especially archaic SD system) was not able to identify a worn/faulty component and simply blames the catalyst.

With 'our' cars(90-02 Accords) that live a mostly sedate life, I would suspect anything else before blaming the catalyst.

ECU/PCMs may also not be programmed to expect a given fault/failure of a component that has aged/worn beyond 100Kmiles. When it is no longer needed to be covered by the manufacture(warranty) they will not bother caring programing to recognize a component out of spec that is not a hard fault.

I've had a few cars that did not recognize a fault with the MAF sensor and fart out a P0420 code. Infuriating. Even clearing the PCM with a scanner has just netted the P0420 popping back up. Pulling the fuse to the ECU/PCM memory does a proper wipe and then, if the ECU/PCM is modern, will usually find the problem and fire out the correct code.

Story time:
Had a Volvo S60 fart out the P0420 code, dumped it off at a dealer to verify problem(s). Because I was busy. "yup you will need a new catalyst, new head, new etc, etc, etc..." No thank you.
On the way home the car started misfiring like a ****. Checked codes, only P0420, cleared codes via scanner, drove again, P0420.
Well a P0420 would NOT cause a misfire problem. So I pulled the PCM fuse. Started the car, warmed it up, and it started to misfire. Before getting back home the CEL was on. Checked codes P0300, P0302, P0420. Kewl.
Pulled the coil packs on #2 and #5, swapped them. Pulled fuse again, drove around CEL came on. Misfire P0300, P0305, P0420. Kewl, bad coilpack. Picked up a new coil pack and set of plugs as they were overdue. Replaced coilpack in the ORLY parking lot and the felt misfire went away. CEL came on halfway home, check codes P0300, P0420. Pulled old plugs(worn) replaced with new. Pulled fuse. Go for a drive to get gas. While driving the car just became a slug, did not want to accelerate and after fueling would not restart. Finally restarted, driving home CEL came on. Checked code P0103. MAF signal high.
Pulled the MAF sensor out, looked like something out of Shreks ear. Blasted it clean, pulled fuse, go for a test drive, accidentally do a burnout. No mo code. Car needed smog by the following month (Calif 5 gas) passed no problem-o.
Had I gone off the original code then I would have spent ~1200 on an un-needed catalyst that was not the problem.

As Honda FSMs usually state, check for any stored codes, pull fuse to clear and drive to verify not an intermittent issue.

I've had similar issues on other makes where the P0420 code pops up and it is NOT the catalyst.

To blame the catalyst is an easy shop/mechnicos way of making a few hundred(or thousand) bucks for 30mins of work. Don't fall for it. Proper diagnostics is always key.

GhostAccord

And even when it is the catalytic converter that has failed. I would look a bit further into why the catalyst failed! It will usually end up being something coming out of the combustion chamber that has caused it to fail prematurely. That usually requires adjustment or replacement of something else as well!

MAD_MIKE

RedTRex

Exactly...... "air leak" is most common, then O2 sensor, then cat.