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Cho Baka
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reply to Gordo74

Re: catalytic converter? P0240

said by Gordo74:

P0420 on my Impala ended up being that there was a vacuum leak in the system near the gas tank. A tube came loose is all.

That makes no sense. Perhaps you have misremembered your code?
--
The talented hawk speaks French.


Anonymous_
Anonymous
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yeah it was p0420 got it rechecked had two entries on it. going to change out the sensor first to see if it fixes that. Since it's way cheaper then paying $1200 to replace it with a factory catalytic converter

New state law requires factory down to the exact model and production code. Other wise automatic fail.

If it was the catalytic converter I would be getting more codes besides the P0420

CEL was tripped when behind a diesel bus that was pouring out smoke.. assuming it was sucking craptastic air from the truck which caused it to trip .

and caused higher emissions from the car = CEL



mattmag
Premium,ExMod 2000-03
join:2000-04-09
NW Illinois
kudos:3

said by Anonymous_:

If it was the catalytic converter I would be getting more codes besides the P0420

What makes you think that? Your assumption in this case is wrong. P0420 is very often a stand-alone code, and requires no other associated failures to enable it.


Anonymous_
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I was behind a bus that was pouring out a lot of smoke, when the CEL came on.



mattmag
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NW Illinois
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1 edit

1 recommendation

said by Anonymous_:

I was behind a bus that was pouring out a lot of smoke, when the CEL came on.

You were behind a smoking bus *twice* to make it come on? You said you already had the code cleared once. And, that's a virtually impossible scenario to cause that code anyway.

What sensor do you plan on replacing on a blind guess? Upstream or downstream? I really don't understand why people want to come up with every reason under the sun why this code sets. There is a converter failure code so you want to replace the oxygen sensor. If a code sets for an cylinder #4 misfire, are you going to replace a headlamp?

I'm being straight here--- BOTH related-bank oxygen sensors MUST BE operating properly for this failure code to occur. The computer is measuring exhaust oxygen content BOTH before AND after the catalyst to determine its efficiency. A malfunctioning O2 sensor strictly prevents this diagnostic cycle from running, and will set a SENSOR failure code, NOT a catalyst code. There are no "false positives" here.

I will add that the best course of repair is proper diagnosis. Get the system tested, preferably by a shop that can scope the components to get the correct picture. Like I said, very high percentage its the converter. Oxygen sensor failure is very rare.


Anonymous_
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said by mattmag:

said by Anonymous_:

I was behind a bus that was pouring out a lot of smoke, when the CEL came on.

You were behind a smoking bus *twice* to make it come on? You said you already had the code cleared once. And, that's a virtually impossible scenario to cause that code anyway.

What sensor do you plan on replacing on a blind guess? Upstream or downstream? I really don't understand why people want to come up with every reason under the sun why this code sets. There is a converter failure code so you want to replace the oxygen sensor. If a code sets for an cylinder #4 misfire, are you going to replace a headlamp?

I'm being straight here--- BOTH related-bank oxygen sensors MUST BE operating properly for this failure code to occur. The computer is measuring exhaust oxygen content BOTH before AND after the catalyst to determine its efficiency. A malfunctioning O2 sensor strictly prevents this diagnostic cycle from running, and will set a SENSOR failure code, NOT a catalyst code. There are no "false positives" here.

I will add that the best course of repair is proper diagnosis. Get the system tested, preferably by a shop that can scope the components to get the correct picture. Like I said, very high percentage its the converter. Oxygen sensor failure is very rare.

I'll just wait tell I need to do the smog test (you bet I going to clear the code before I get the test done)

if it passes then it's a faulty SENSOR. if it fails I get it fixed
--
Well, does your car at least turn into something else? Sometimes I turn it into a trashcan. Hmm...

telco_mtl

join:2012-01-06
reply to mattmag

said by mattmag:

said by Anonymous_:

If it was the catalytic converter I would be getting more codes besides the P0420

What makes you think that? Your assumption in this case is wrong. P0420 is very often a stand-alone code, and requires no other associated failures to enable it.

exactly, like i just posted, faulty cats threw that code on my both grand prix. same car as the impala, and those were the only codes i had


Gordo74
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join:2003-10-28
Monroeville, PA
reply to Cho Baka

said by Cho Baka:

said by Gordo74:

P0420 on my Impala ended up being that there was a vacuum leak in the system near the gas tank. A tube came loose is all.

That makes no sense. Perhaps you have misremembered your code?

I never said it made sense, but repairing the vacuum leak made it go away and MPG returned to normal.


Anonymous_
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4 edits

mileage is sloppy been getting 18MPG city(@near highway speeds 45-65mph ) and 23MPG on the freeway.(very hilly though)

before the fuel regulator went out I was getting 17/22
when the fuel regulator was dead 9MPG/15MPG
(No visible smoke with the "rich mixture")

Not getting any visible smoke from the tail pipe.
using 1 qt of oil every 2,000-2100 miles which is at manufacture specification.

I use 89 octane fuel
engine runs quieter over all with this fuel.

engine Is running warmer then normal (but still with in the normal accepted rage aka the middle)

But I think it still should be less since it is winter and is fairly cold outside mid 40's

Ones in bold might be the possible issue

A code P0420 may mean that one or more of the following has happened:
Leaded fuel was used where unleaded was called for

A damaged or failed oxygen sensor (HO2S)
Downstream oxygen sensor (HO2S) wiring damaged or connected improperly
The engine coolant temperature sensor is not working properly
Damaged or leaking exhaust manifold / catalytic converter / muffler / exhaust pipe
Retarded spark timing
The oxygen sensors in front and behind the converter are reporting too similar of readings
Leaking fuel injector or high fuel pressure


Cylinder misfire
Oil contamination



Cho Baka
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That is a funny list. I googled it, and in the first hit it seems to have been posted in the comments on an Amazon sale for an O2 sensor.

The second link, »www.obd-codes.com/p0420 , has these 2 gems:
"Overall probably the biggest mistake vehicles owners make when they have a P0420 code is to simply replace an oxygen sensor (H02S). It is important to do proper diagnosis so you're not wasting money replacing parts unnecessarily.

We strongly recommend that if you need to replace the catalytic converter that you replace it with an OEM unit."

Go ahead and replace that sensor if you want. It isn't my money you are burning.
--
The talented hawk speaks French.


Formeister

join:2000-10-28
Somers, CT

P0420 Catalytic efficiency below threshold value.

My daughter's 1998 Accord threw this code twice, about two years apart. The first time I guessed and didn't test the 02 sensor, just replaced the easiest sensor to reach, the one after the cat and code cleared. Two years later, same code. Naturally, I replaced the inlet O2 sensor this time. Code cleared. Car sold three years later with original cat and 240K miles.

The cat converter efficiency can only be measured by two O2 sensors: in and out.

So, I would test each O2 sensor as they are so easy to remove, before I'd spend a bunch on a new cat.

BTW, there are thermal tests that can be done on a cat to determine if it's functioning correctly but most home owners don't usually have the thermocouple sensors and meters.

Cats do fail, I've just never seen it on many high (>200K mile) cars that I have driven, ymmv.



Anonymous_
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1 edit
reply to Cho Baka

said by Cho Baka:

That is a funny list. I googled it, and in the first hit it seems to have been posted in the comments on an Amazon sale for an O2 sensor.

The second link, »www.obd-codes.com/p0420 , has these 2 gems:
"Overall probably the biggest mistake vehicles owners make when they have a P0420 code is to simply replace an oxygen sensor (H02S). It is important to do proper diagnosis so you're not wasting money replacing parts unnecessarily.

We strongly recommend that if you need to replace the catalytic converter that you replace it with an OEM unit."

Go ahead and replace that sensor if you want. It isn't my money you are burning.

Thanks the light went off, after I smacked the catalytic converter, with a rubber mallet.
saved $1400 doing that. 150miles+ no light

Now I have to deal with the thermostat... since it's overheating now, to keep it under the 1/2 point I drove it 150 miles with the heater on and windows & moon roof open)

coolent is full maybe it has some air in the system or thermostat is failing ?

yes it has coolant in it


rockotman
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Hmmm.... a clogged cat can also cause excessive back-pressure which can lead to overheating.



Anonymous_
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3 edits

said by rockotman:

Hmmm.... a clogged cat can also cause excessive back-pressure which can lead to overheating.

100% "clear" air comes from the tail pipe. a lot of it
before I was getting 22-23mpg highway

Now gas mileage shot up was getting 35MPG (300miles round trip total) (computer claimed 45MPG average though.)
80 to 99 (inst mpg)


Lagz
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join:2000-09-03
The Rock

Hmmm .. p0420 and a rough idle.
»03 impala idle issues
2 + 2 = 4



Anonymous_
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that was the fuel regulator



Cho Baka
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said by Anonymous_:

that was the fuel regulator

That killed the cat.
--
The talented hawk speaks French.


rockotman
...Blown On The Steel Breeze
Emerging Research
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said by Cho Baka:

said by Anonymous_:

that was the fuel regulator

That killed the cat.

I thought curiosity killed the cat.

I mentioned a failed cat that I experienced above. The dealer service manager at the dealer thought that a failed ignition module that I had experienced a few months earlier which turned my 4-cylinder into a 2-cylinder on Christmas day the previous year may have lead to my premature cat failure.

As I loaded the family into the car on Christmas day to go visit relatives, the car ran extremely rough, so I parked it and we all jumped into my son's Scion to go visit family. I can tell you that 6'1" does not fit well in the back of a tC.

Anyway, the next day I dropped my "2-cylinder" off at the dealer (1 mile from the house) to get it fixed under warranty. It was, as I suspected, the ignition module. It was dumping raw fuel into the exhaust for only about the 5 or 10 minutes it took to get to the dealer. But the following March, the cat failed.
--
Shine on you crazy diamond...


Anonymous_
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Click for full size
said by rockotman:

said by Cho Baka:

said by Anonymous_:

that was the fuel regulator

That killed the cat.

I thought curiosity killed the cat.

I mentioned a failed cat that I experienced above. The dealer service manager at the dealer thought that a failed ignition module that I had experienced a few months earlier which turned my 4-cylinder into a 2-cylinder on Christmas day the previous year may have lead to my premature cat failure.

As I loaded the family into the car on Christmas day to go visit relatives, the car ran extremely rough, so I parked it and we all jumped into my son's Scion to go visit family. I can tell you that 6'1" does not fit well in the back of a tC.

Anyway, the next day I dropped my "2-cylinder" off at the dealer (1 mile from the house) to get it fixed under warranty. It was, as I suspected, the ignition module. It was dumping raw fuel into the exhaust for only about the 5 or 10 minutes it took to get to the dealer. But the following March, the cat failed.

replaced the radiator cap as it had caked on dirt preventing it from working correctly. I got a thermostat as well but I have not installed it Only got it because they only had a few left in stock.

coolant is clean so it does not need to be changed


Gordo74
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join:2003-10-28
Monroeville, PA

What does the radiator cap have to do with the issue at hand? A good cleaning of it would have been fine rather than replacing it.

And you bought a thermostat just because they only had a few left in stock? You realize places like rockauto.com are cheaper and ship to your door, yes? Why buy something when you don't need it?

For someone who complains so much about how the car "costs you too much" (other thread), you sure do love throwing needless money at it.



Anonymous_
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1 edit

said by Gordo74:

What does the radiator cap have to do with the issue at hand? A good cleaning of it would have been fine rather than replacing it.

And you bought a thermostat just because they only had a few left in stock? You realize places like rockauto.com are cheaper and ship to your door, yes? Why buy something when you don't need it?

For someone who complains so much about how the car "costs you too much" (other thread), you sure do love throwing needless money at it.

Thermostat is going to be returned as the new cap fixed the issue.
If you see the rubber seal is torn and cracked .
That probably means it has a poor seal on it.

Car sits at the under the middle line even with the a/c on full blast.

Yes rocketauto is great but if you need the item by tomorrow it will cost the same or more to get it.
Expand your moderator at work