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If P0420 is present then:
Topic Started: Apr 4 2012, 08:44 PM (5,281 Views)
Woodie
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There was no room for an extender whatsoever on mine, wires were already up against the metal of the center tunnel. I got a 45° angle extender.

http://www.etektuning.com/42-draft-o2-sensor-spacer/

Here's a 90° one: http://tinyurl.com/7qh4dcb
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Dayle1960, when you want to know the answer, you climb to the top of a tall mountain in Tibet, wearing nothing but a loin cloth and Nikes, and ask some guy in a white robe, sitting on a rock in a cave, eating a Snickers Bar, or send an email to GMF member #15, aka pacapo, aka Phil N Ed on TeamSwift.

For those of you who are, or were in the Navy, I believe the appropriate preface phrase is, "And this is no sh!t."


Geo Glenn:

"What is the difference between the catalytic converters legal for sale in the State of California, and the others?

Rumor, and the Factory Service Manual says that OEM cats have more of what makes them work on the inside, and the OEM will last longer. Is this true of the California aftermarket versions?

I have a code P0420. FSM says dead cat. I haven't put the voltmeter on the downstream (recently replaced) O2 sensor. When I do, it will probably confirm catalytic converter inefficiency.

WTF?, over."

Pacapo:

"The problem was, smog techs were being blamed so they complained to Sacramento. They investigated, and the aftermarket catalytic converters (cats) have less catalyst so they keep the costs down.

Most people don't keep the car and so it wasn't being noticed.

The smog test results showed that the 48 State cats were inferior and Sacramento passed a law making the manufacturers put the right amount of catalyst into the cats being sold in California.
At first, it was an unpopular move, as the manufacturers reacted by charging a lot for the California cat.
Then, word spread that the CARB cat (California Air Resources Board) was a superior product which is supposed to last 70,000 miles if put on a clean burning engine.

The bottom line? If you can afford one, the CARB cat is the way to go. I put 3 on our cars last year. $150 out the door, installed at a muffler shop in L.A. that I've used for years.

I want my cars to pass smog and I don't want to have to change out a cat after only 20,000 miles like the old aftermarkets. Those things were junk."



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dayle1960
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Fastest Hampster EVER

This adds a new dimension to my search for the fix to the elusive P0420 problem. Seems to me that there is some sort of catalyst within the cat. I wonder if the catalyst gets burned up or covered with soot. I think there is only a speck of catalyst inside of the cat, yet, I ponder if the catalyst is at fault or is the sensor the bad part of the problem. Still trying to figure this out.

Anybody heard from mwebb lately?
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dayle1960
Apr 10 2012, 01:12 PM
This adds a new dimension to my search for the fix to the elusive P0420 problem. Seems to me that there is some sort of catalyst within the cat. I wonder if the catalyst gets burned up or covered with soot. I think there is only a speck of catalyst inside of the cat, yet, I ponder if the catalyst is at fault or is the sensor the bad part of the problem. Still trying to figure this out.

Anybody heard from mwebb lately?
As much as has been said above, the bottom line is that the downstream O2 sensor exists only to tell you when the catalytic converter is below the threshold of efficiency.

A properly functioning upstream O2 sensor will have voltage fluctuations indicated on an osciliscope, or lacking such equipment, a voltage variation on your Scangauge or Ultragauge.

DTC P0420 will be indicated when the downstream O2 sensor has a voltage fluctuation like the upstream O2 sensor. A flatline voltage indication on the downstream O2 sensor is what will be seen when the catalytic converter is doing its' job.

If the last catalytic converter you bought fixed DTC code P0420, and it was not a California Air Resources Board approved version, it probably has already failed, and the P0420 code returned.

Pacapo knows. He's lived in California for years. You get what you pay for. I'll be installing CARB catalytic converters on my vehicles.
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Johnny Mullet
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Fear the Mullet

Walker replacement cat will pass.
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ascensions
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Je conduis une petite voiture.

Geo Glenn
Apr 10 2012, 02:03 PM
the bottom line is that the downstream O2 sensor exists only to tell you when the catalytic converter is below the threshold of efficiency.
Please cite a source, I disagree.
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ascensions
Apr 10 2012, 05:31 PM
Geo Glenn
Apr 10 2012, 02:03 PM
the bottom line is that the downstream O2 sensor exists only to tell you when the catalytic converter is below the threshold of efficiency.
Please cite a source, I disagree.
Factory Service Manual. If you don't have one. Get one. We'll talk.

Read. Test on Friday.

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ascensions
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Je conduis une petite voiture.

According to the document posted, it states in the second paragraph under 02-2, that it does have a role (though limited) in fuel delivery.

Quote:
 
In addition to catalyst monitoring, the HO2S 2 heated oxygen sensor has a limited role in controlling fuel delivery. If the HO2s 2 signal indicates a high or low oxygen content for an extended perior of time while in closed loop, the PCM will adjust fuel delivery slightly to compensate.


Which is, based on what I've found typical. Between 1-5% difference.

So saying it only monitors catalyst function is incorrect.
Edited by ascensions, Apr 10 2012, 07:59 PM.
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ascensions
Apr 10 2012, 07:56 PM
According to the document posted, it states in the second paragraph under 02-2, that it does have a role (though limited) in fuel delivery.

Quote:
 
In addition to catalyst monitoring, the HO2S 2 heated oxygen sensor has a limited role in controlling fuel delivery. If the HO2s 2 signal indicates a high or low oxygen content for an extended perior of time while in closed loop, the PCM will adjust fuel delivery slightly to compensate.


Which is, based on what I've found typical. Between 1-5% difference.

So saying it only monitors catalyst function is incorrect.
Fine. Test passed. :thumb Bonus points awarded. ;) I was aware of the fuel trim function according to the FSM. :deal

Dayle1960 has a DTC P0420. The cure is a new catalytic converter. The best catalytic converters are OEM or CARB compliant. The fuel trim function of the downstream O2 sensor has no relevance to the DTC.

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dayle1960
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Fastest Hampster EVER

Oh, goody, goody!!!!!!!!!!

Now all I'd like to know is why the cat failed????????

Did the catalyst crap out or did I have contamination from another source?

How can I determine which one of these scenarios is the real cause of my P0420?

BTW, GG, your research on this issue had been enlightening. I have questions and you supply the direction I should look. I appreciate your hard work.

Although JM has stated that I need a new cat in a couple of previous posts, I wanted to find out how/why the cat failed. It bugs me that something so new failed. But after reading other folks explainations, I am getting closer to my answer.

Thanks to everyone who has chimed in. All I want to do with this thread is peel away the curtains and let newbies understand how to track down a problem and why that problem exists. I suppose if I were any kind of mechanic I would invest in a FSM. But such is life, I like to interact with other metro enthusiasts and ya'll are kind enough to let me see inside of you thinking processes. That is priceless information.

Thanks
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JM's experience with cats is that Bosal is junk. He said Walker is good. I'm not sure what brand cat you got the last time. The California smog techs get the most and best information. Pacapo has the inside skinny on that. He's got OBD1 smog certs.

You can get your girl a cubic zirconia ring, and ask her to marry you. It will most likely get you down the isle. One of these days, she'll run it in for appraisal. That's the day you get the GF0420 code.

The cats look the same. It's what's inside that makes the difference. Mwebb has mentioned dog schnidt cats, or something to that effect. Run the FSM diagnostics and tests. You'll find the true answer.

To paraphrase pacapo. "A clean running engine with a CARB compliant cat will last 70,000 miles. The others will last 2 years."

As to why the cat failed? Did I mention dog schnitz?

I'm going to buy you a Factory Service Manual for your birthday, or something there Dayle1960. Your Haynes or Chilton Manual can then serve it's true function in life. Cleaning up oil spots on the floor.

:lol
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mwebb
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FOG

go to GM Mode6 search for your car then your system , read up on the TID $01 test
for the cat converter

on Geo Metros
the rear 02 sensor has zero authority for fuel trim , it has no effect at all on fuel trim .

do not use the spacers
just unscrew the rear 02 from the exhaust and wrap it in a shop rag and place it in the upper right strut top area
gently
if you break the thimble it may code . depends on the way you break it , do not let it get water on it self .
Posted Image

red is front 02 sensor green is rear , very bad cat at cruise , every thing up to temp - front 02 sensor is also bad
the front 02 sensor is "new"
without a scope
you can not see this

you can approximate this with a graphing scan tool
Posted Image
a v6 , both front 02 sensors
unlike a geo metro
that system does trim on the rear 02 sensors - there is a break in the exhaust between the front and rear 02 sensors
atmospheric air gets to the rear 02 sensor and it reports a different fuel correction than the front
use measuring block 37 and 38 to see the delta value , should be zero

in vw / audi speak
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mwebb
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FOG

go to GM Mode6 search for your car then your system , read up on the TID $01 test
for the cat converter

on Geo Metros
the rear 02 sensor has zero authority for fuel trim , it has no effect at all on fuel trim .

do not use the spacers
just unscrew the rear 02 from the exhaust and wrap it in a shop rag and place it in the upper right strut top area
gently
if you break the thimble it may code . depends on the way you break it , do not let it get water on it self .
Posted Image

red is front 02 sensor green is rear , very bad cat at cruise , every thing up to temp - front 02 sensor is also bad
the front 02 sensor is "new"
without a scope
you can not see this

you can approximate this with a graphing scan tool
Posted Image
a v6 , both front 02 sensors
unlike a geo metro
that system does trim on the rear 02 sensors - there is a break in the exhaust between the front and rear 02 sensors
atmospheric air gets to the rear 02 sensor and it reports a different fuel correction than the front
use measuring block 37 and 38 to see the delta value , should be zero

in vw / audi speak

Posted Image
scan data , graphed , in a Geo metro
mine
the front 02 sensor is red trace
rear 02 sensor is blue trace
vehicle speed is orange , notice that the rear 02 sensor does not begin to report until AFTER the mighty geo metro exceeds
50mph

that is because the rear 02 sensor heater does not get switched on until
50mph , why ? who knows who cares , it is , remember when you are testing them .

notice the frequency that the front 02 sensor reports in is much faster than the rear 02 sensor
this is what a "good" cat converter will do
with a bad cat the front and rear 02 sensor s will cycle in unison ,
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ascensions
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Je conduis une petite voiture.

Quote:
 
50mph , why ? who knows who cares , it is , remember when you are testing them .


It doesn't turn on till 50 MPH because there's not enough flow to accurately gather data, and more importantly a catalytic converter doesn't begin to function properly until heated to a certain temperature, which likely, won't occur until you're driving at high-way speed, thus 50 MPH.
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mwebb
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FOG

ascensions
Apr 11 2012, 08:19 AM
Quote:
 
50mph , why ? who knows who cares , it is , remember when you are testing them .


It doesn't turn on till 50 MPH because there's not enough flow to accurately gather data, and more importantly a catalytic converter doesn't begin to function properly until heated to a certain temperature, which likely, won't occur until you're driving at high-way speed, thus 50 MPH.
good guess ..
but no
correct answer is , cold water
which is an exhaust by product

N2 H20 and C02 in a perfect world

will touch the rear 02 sensor thimble and if the 02 sensor heater is "on" the thimble will
crack from thermal shock , so Mr ECM does not allow the rear 02 heater to switch on until the water in the exhaust is hot vapor

this info is not really needed when testing this system

unless your testing shows the rear 02 sensor signal flatlined at 1.2 volts ... before you condemn the rear 02 sensor drive the car and exceed 50 mph , if the car is "hot" when you drop below 50mph the ECM does not switch the rear 02 sensor heater off until

the engine is switched off and the engine gets "cold" from non use, if the engine is restarted before it gets "cold" the rear 02 sensor remains active .

Hot and cold values are determined by the ECM
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