Check Engine light - code P0420

aarcuda69062 > wrote in news:nonelson-
:

> In article
>
> m>,
> Marsh Monster > wrote:
>

>
> Uh, no. the computer 'thinks" that the cat can't store oxygen as
> it is supposed to.
>>
>> IF.........too much fuel was entering the converter....and the
>> converter is not CAPABLE, for whatever reason, to burn off
>> the excess to a point that lowers the rear reading to within
>> factory parameters for an efficient catalytic activity.....then THAT
>> code WILL set.
>
> You really-REALLY need some driveability classes.
> i.e., why don't cat efficiency codes set when the engine is
> operated at wide open throttle (rich exhaust)?
>



It doesn't take long for even somebody not in the industry to find out how
a P0420 is set. It is set when the catalytic converter fails the ECM's cat
efficiency test.

The test is, from my readings, this: The ECM commands rich for 5 seconds to
drain the cat of oxygen. Then it commands lean for five seconds, measuring
how long it takes for the secondary sensor to start flip-flopping. If the
rear sensor flip-flops too soon, the ECM assumes the cat's unable to store
sufficient oxygen, and sets the P0420.

I also understand that there are certain unusual circumstances that can
lead to a P0420 even when the cat's fine. These would include air leaks
into the exhaust after the primary sensor, or before the secondary. Also,
certain Honda models (I know the OP's car is a Toyota) have problems with
the igniter electrical connections that can lead to a false P0420.

--
Tegger

Mark > wrote:
>Thanks everyone for your responses. Though I am still confused at this
>point. I would atleast like to get an idea of whether this is caused
>by my replacement of flexpipe/cat. converter or the fuel injection
>service. Without taking any guesses, can somebody point me in the
>right direction based on their experience? Could a fuel injection
>service indeed cause the CEL with reason code P0420 - catalytic
>converter efficiency low?

The computer looks at the results of the two oxygen sensors, and if the
difference is out of range, it throws this code.

This code COULD be because the converter isn't any good, or isn't correct.
Or it COULD be because a lot of junk was thrown into the converter briefly
(maybe during the injection cleaning) and it couldn't deal with it.

A scan tool that can actually look at the sensor readings will tell you
which of these is the case.

Alternately you can just reset the code and see if it comes back. If it
comes back, it wasn't due to the injector cleaning.

But right now you don't have enough information to be sure.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On Dec 4, 10:05 am, (Scott Dorsey) wrote:
>
> Alternately you can just reset the code and see if it comes back. If it
> comes back, it wasn't due to the injector cleaning.
>
So if I reset the code and it comes back, then it is not due to fuel
injection cleaning? I could use this approach to eliminate this
service and the it would point to maybe a damaged converter?

======
======
aarcuda69062
((spewed forth more insight into his inability to))
((comprehend simplified systems with these ))
((insertions to MarshMonster))
..
..
Uh, no. the computer 'thinks" that the cat can't store oxygen as
it is supposed to.
..
..

=======
=======
On Dec 4, 5:54 pm, Mark >
So if I reset the code and it comes back, then it is not due to fuel
injection cleaning? I could use this approach to eliminate this
service and the it would point to maybe a damaged converter?

=========
=========

What IF....that cleaning busted loose enough crap THROUGHOUT the
system and SOME this CRAP is now BAKED on yer sensor/sensors??


but......

you do what you want........

I'VE DONE TOLD YER DUMBASS TO CARRY IT TO THE FLUSH DUDE
AND GIT IT LOOKED AT FOR FK'N FREE!!!!!!!!!!!

but........

clear the codes if you want.....
then....if the codes comeback......
go blame the dude that put the convertor on.....

jest do this when you do......

make sure you tell HIM.....that system was flushed AFTER
the convertor was put on.........i mean........

we do wanna be HONEST here .......rite??






~:~
MarshMonster
~takes a toke.......wonders if anyone here has been smart enough
to google this subjest.........takes a toke......lhao~
~:~

On Dec 4, 5:54 pm, Mark > wrote:
> On Dec 4, 10:05 am, (Scott Dorsey) wrote:
>
> > Alternately you can just reset the code and see if it comes back. If it
> > comes back, it wasn't due to the injector cleaning.
>
> So if I reset the code and it comes back, then it is not due to fuel
> injection cleaning? I could use this approach to eliminate this
> service and the it would point to maybe a damaged converter?

===============
================

The flush did it.

there......i said it.......now i feel better.




~:~
marsh
~smokes a big ole hooter.....~
~:~

In article

m>,
Marsh Monster > wrote:

> ======
> ======
> aarcuda69062
> ((spewed forth more insight into his inability to))
> ((comprehend simplified systems with these ))
> ((insertions to MarshMonster))
> .
> .
> Uh, no. the computer 'thinks" that the cat can't store oxygen as
> it is supposed to.
> .
> .
> .
> You really-REALLY need some driveability classes.
> i.e., why don't cat efficiency codes set when the engine is
> operated at wide open throttle (rich exhaust)?
> .
> Workin' on a Sunday so you can someday afford a 5 gas?-
> =========
> =========
> Concerning youre first statement...........where does this
> Cat get the oxygen from, and exactly where does it store it ??

It's not surprising that you wouldn't know this. <snicker>
The answer to the first part is; the atmosphere (duh), which is
usually around 21% oxygen but it varies depending on how much
dope *you're* smoking in proximity.
You know, that air fuel ratio thing.
The answer to the second part is; the Cerium wash coat.
Like I said, you need some classes because this stuff is (well)
over a decade old.

>
>
> Concerning your second statement........hmmmmm
> I would jest refer you to YOUR 1 SPARK EVERY 3 SECONDS
> ON A SPARK PLUG post...........but .........
> ok.......i'll GIVE you one more insight into BASIC computer
> strategy....
> by simply asking you.........
>
> YOU...rectom the OE designers figured vehicles would always run
> at the SAME temp, SAME rpm, SAME throttle setting...etc..etc...
> or YOU rectom.......THEY...were a bit smarter than YOU....and
> THEY......made the "black box" able to understand that variables
> exist under different operating parameters??

This has nothing to do with whether or not I am smarter than the
OE engineers. Oxygen sensors DO NOT react to raw fuel as you
implied in your post, the post cat O2 will not set a efficiency
code just because an engine is/was over fueled as your post
implied.

> OH....and.....jest like the other thread.....don't appologize....
> jest say....."oops" again..

Speaking of other posts, do you want to take another shot at
spelling 'definitely'?
(hint; there is no "a")

> As to yer last question...........I don't work Sundays.

Well, you posted on Sunday and mentioned that you were watching
the "4 gass" while fiddling with the throttle body.
So, the real case here is; you felt need for a clever buzz word
to lend some credibility to your asinine statements.

So, tell me about your "4 gass", what brand is it? Is it a
non-dispersive infra red or flame ionization bench?
Does it have constant volume sampling? Does it allow for
corrected NOx sampling?

>
>
> ~:~
> marsh
> ~sips his shroom juice......mmmmm.......good stuff~
> ~:~

In article

>,
Marsh Monster > wrote:

> =======
> =======
> On Dec 4, 5:54 pm, Mark >
> So if I reset the code and it comes back, then it is not due to fuel
> injection cleaning? I could use this approach to eliminate this
> service and the it would point to maybe a damaged converter?
>
> =========
> =========
>
> What IF....that cleaning busted loose enough crap THROUGHOUT the
> system and SOME this CRAP is now BAKED on yer sensor/sensors??

How about; there would be O2 sensor performance codes setting
instead of cat efficiency codes. <sheesh>

>
> but......
>
> you do what you want........
>
> I'VE DONE TOLD YER DUMBASS TO CARRY IT TO THE FLUSH DUDE
> AND GIT IT LOOKED AT FOR FK'N FREE!!!!!!!!!!!

Because even though there are thousands of fuel injector flush
services done every day, there is yet no industry wide problem
with those services causing catalytic convertor failures in spite
of the fact that aftermarket convertors are known to be less than
50% efficient (which is no where near good enough) right out of
the box?

> but........
>
> clear the codes if you want.....
> then....if the codes comeback......
> go blame the dude that put the convertor on.....

For trying the cheap way out.

> jest do this when you do......
>
> make sure you tell HIM.....that system was flushed AFTER
> the convertor was put on.........i mean........

Do these convertors come with a warning that injector flushing is
not allowed and/or will void any warranty?
(feel free to post a copy)

> we do wanna be HONEST here .......rite??

Why, you're not.

>
>
>
>
>
> ~:~
> MarshMonster
> ~takes a toke.......wonders if anyone here has been smart enough
> to google this subjest.........takes a toke......lhao~

Some of us don't need to because we actually do it every day for
a living.

So Mr. Doobie, how many times a day do you use Google to repair
your customers vehicles?

In article >,
Mark > wrote:
>On Dec 4, 10:05 am, (Scott Dorsey) wrote:
>>
>> Alternately you can just reset the code and see if it comes back. If it
>> comes back, it wasn't due to the injector cleaning.
>
>So if I reset the code and it comes back, then it is not due to fuel
>injection cleaning? I could use this approach to eliminate this
>service and the it would point to maybe a damaged converter?

Umm... yes. The fuel injection cleaning isn't doing any permanent damage
to anything. It's just dumping a lot of crap out of the tailpipe for a
short while.

A damaged (or incorrect) converter is permanent damage.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Thanks everyone for your insights, suggestions and advice. This forum
offers a lot of expert advice from different people with different
point of views and experiences, and thats what makes it so valuable. I
appreciate everyone taking their precious time to respond.

I just wanted to post an update that my check engine light went away
this evening. I did not do anything yet. I went to work in the morning
and the light was on. When returning from work, I turned on the car
and the light was gone. I have made a couple of short trips since then
and the light has not come back on. Based on this occurence, I would
again have to lean on the experts here to understand what this means,
and if it may have temporarily disappeared and could return again.

Another problem that I didn't bring up earlier, as I did not want to
divert attention from the CEL problem, was that my fuel mileage had
dropped since I had replaced the catalytic converter. Previously I
would get about 24mpg and after replacing the converter I am getting
around 20mpg. I noticed the drop in mileage after replacing the cat
and before the fuel injection service. I have to ask this dumb
question, but can the replacement of the cat. converter cause a drop
in the mileage too (i.e. if I have a bad cat.) ?

Thanks everyone for your help.