oxygen sensor

I've got a 98 4cyl 4Runner 4x4 which I've recently pulled off a P0136
code. From the information I've gathered it is the oxygen sensor
located after the cat. I've cleared the code and I'm waiting to see
if it comes back. I've read however that bad readings from the 2nd
sensor could indicate problems with the 1st sensor at the manifold as
it has more influence on fuel/air ratios... even though it isn't the
one generating the codes. The truck has 170000 kms and the mileage
isn't as good as it used to be, but it seems to be running fine in all
other regards. Does it make sense to replace these sensors just as a
part of routine maintenance? (they are still original)

Curious as to what others have experienced. Thanks in advance.

Randy

"yotaman" <randyvp@gmail.com> wrote in message
news:1170385012.255537.212770@q2g2000cwa.googlegroups.com...[color=blue]
> I've got a 98 4cyl 4Runner 4x4 which I've recently pulled off a P0136
> code. From the information I've gathered it is the oxygen sensor
> located after the cat. I've cleared the code and I'm waiting to see
> if it comes back. I've read however that bad readings from the 2nd
> sensor could indicate problems with the 1st sensor at the manifold as
> it has more influence on fuel/air ratios... even though it isn't the
> one generating the codes. The truck has 170000 kms and the mileage
> isn't as good as it used to be, but it seems to be running fine in all
> other regards. Does it make sense to replace these sensors just as a
> part of routine maintenance? (they are still original)
>
> Curious as to what others have experienced. Thanks in advance.
>
> Randy
>[/color]

If you have a volt meter, with the engine warmed up, rev the engine to
between 2,000 and 3,000 RPM and check voltage output from Bank 1 Sensor 2 O2
sensor. It should fluctuate from less than .4 volts to more than .5 volts.
If it doesn't, the O2 sensor is bad. If it does, check for an open or short
in the circuit between the O2 sensor and the computer. Bank 1 Sensor 2 is
the sensor located after the cat. If you have a single exhaust and cat., it
is the only sensor. If you have 2 exhausts/cats, it is on the side that
contains cylinder #1.
--

Ray O
(correct punctuation to reply)

[email]johngdole@hotmail.com[/email] wrote:
[color=blue]
> I'd recommend Bosch planar type sensors. Best in class stuff. I
> managed to rid the P0420 code with new Bosch sensors when TSB
> suggested replacing the cat (and leaving the sensors alone!)
>
> See:
> [url]http://www.boschautoparts.com/Products/OxygenSensors/[/url][/color]

Crap!!!

the number two oxy sensor is usualy used to determine how well the cat is
working . for example if you could see the sensor flow grafs the number
one sensor would bee totally diff from the # 2 sensor if working right if
they look the same or close then the cat is not working at the price of
the sensors i would just replace the defective one you'll need it for
emission testing. don't forget your engine management runs through a
comuter so garbage in garbage out

P0136
O2 Sensor Circuit Malfunction (Bank 1 Sensor 2)


My personal thought on the O2 Sensors is that they are prone to actual
failure before they are likely to give an accurate report of something else
wrong.

They live in an extremely hostile environment, and they literally cook to
death. I'd guess that the age and mileage on your 4Runner means that the
sensors have cooked.

I'm not certain, but I _think_ there is an expected life span of 100k miles,
and you are sneaking up on that number -- you are a bit shy of the spec, if
I got the spec right. In my estimation, you replaced the right part at the
right time, and your troubles should be over. Well, THIS trouble is over,
the next trouble is yet to begin.






"yotaman" <randyvp@gmail.com> wrote in message
news:1170385012.255537.212770@q2g2000cwa.googlegroups.com...[color=blue]
> I've got a 98 4cyl 4Runner 4x4 which I've recently pulled off a P0136
> code. From the information I've gathered it is the oxygen sensor
> located after the cat. I've cleared the code and I'm waiting to see
> if it comes back. I've read however that bad readings from the 2nd
> sensor could indicate problems with the 1st sensor at the manifold as
> it has more influence on fuel/air ratios... even though it isn't the
> one generating the codes. The truck has 170000 kms and the mileage
> isn't as good as it used to be, but it seems to be running fine in all
> other regards. Does it make sense to replace these sensors just as a
> part of routine maintenance? (they are still original)
>
> Curious as to what others have experienced. Thanks in advance.
>
> Randy
>[/color]

We've had this discussion before, and I think this is the point that I was
getting wrong.

Our discussion was in regards to P0420, Catalyst System Efficiency Below
Threshold (Bank 1), where I insisted that this meant the after-CAT sensor
had failed. My position was that this code said that whatever was going into
the CAT was good, but what came out was expected to be different, but
wasn't.

During the discussion, I looked for the P0136, but did not recognize it as
the code for the after CAT sensor. I submit that you were telling me that
this code was the one that would come up under the conditions we were
talking about at the time, and I argued against you. Now I see what you were
saying, and I accept your argument by the way.

In layman's terms, can you explain why the after CAT sensor can generate two
different codes in entirely different code families? Most codes are grouped
by family, and there might be failures of a component that can appear as
different codes within the family, but in this instance there are multiple
codes that a single component can generate that are not in the same code
family.

I come from a troubleshooting background, and have over 20 years in various
kinds of troubleshooting. Admittedly, my trade experience is not automotive,
but troubleshooting is troubleshooting until one needs to delve relatively
deeply into the affected systems. My point is, the engineers that I've
worked with have a descernable method to their collective madness, and
having the same component spit out a P0136 or a P0420, depending on
variables I don't fully understand is a bit confusing.

I'm asking if you can help me get my arms around the variables. I have a
good grasp of what the codes are telling me, and I'd be looking at the same
part(s) if either of these two codes came up, but I don't understand why the
code families are so far removed from one another for what is in essence a
failure report of the same component. Well, one report says (without getting
bogged down with detail) the sensor isn't working, the other says the part
that the sensor is looking at isn't working.



BY WAY OF EXAMPLE
The Evaporative Emissions Control System produces a range of codes that are
all within a family. A poorly installed gas cap can give a "system
malfunction" code, a "system gross leak" code, and a "system minor leak"
code. I concede the point that there can be other problems that give these
codes, but my point is that all of the problems that I know about relative
to the system all generate a grouping of codes in the OBD II system. Several
components within the system give a code that is in the family. Relative the
CAT, it appears that there is one component that can give a code that is in
at least two families.






"Ray O" <rokigawaATtristarassociatesDOTcom> wrote in message
news:a196d$45c2c087$47c2b532$28144@msgid.meganewsservers.com...[color=blue]
>
> "yotaman" <randyvp@gmail.com> wrote in message
> news:1170385012.255537.212770@q2g2000cwa.googlegroups.com...[color=green]
>> I've got a 98 4cyl 4Runner 4x4 which I've recently pulled off a P0136
>> code. From the information I've gathered it is the oxygen sensor
>> located after the cat. I've cleared the code and I'm waiting to see
>> if it comes back. I've read however that bad readings from the 2nd
>> sensor could indicate problems with the 1st sensor at the manifold as
>> it has more influence on fuel/air ratios... even though it isn't the
>> one generating the codes. The truck has 170000 kms and the mileage
>> isn't as good as it used to be, but it seems to be running fine in all
>> other regards. Does it make sense to replace these sensors just as a
>> part of routine maintenance? (they are still original)
>>
>> Curious as to what others have experienced. Thanks in advance.
>>
>> Randy
>>[/color]
>
> If you have a volt meter, with the engine warmed up, rev the engine to
> between 2,000 and 3,000 RPM and check voltage output from Bank 1 Sensor 2
> O2 sensor. It should fluctuate from less than .4 volts to more than .5
> volts. If it doesn't, the O2 sensor is bad. If it does, check for an open
> or short in the circuit between the O2 sensor and the computer. Bank 1
> Sensor 2 is the sensor located after the cat. If you have a single
> exhaust and cat., it is the only sensor. If you have 2 exhausts/cats, it
> is on the side that contains cylinder #1.
> --
>
> Ray O
> (correct punctuation to reply)
>[/color]

"Jeff Strickland" <crwlr@verizon.net> wrote in message
news:ekrxh.384$384.136@trnddc05...[color=blue]
> We've had this discussion before, and I think this is the point that I was
> getting wrong.
>
> Our discussion was in regards to P0420, Catalyst System Efficiency Below
> Threshold (Bank 1), where I insisted that this meant the after-CAT sensor
> had failed. My position was that this code said that whatever was going
> into the CAT was good, but what came out was expected to be different, but
> wasn't.
>
> During the discussion, I looked for the P0136, but did not recognize it as
> the code for the after CAT sensor. I submit that you were telling me that
> this code was the one that would come up under the conditions we were
> talking about at the time, and I argued against you. Now I see what you
> were saying, and I accept your argument by the way.[/color]

The way to learn about how something works is to read or listen to what
someone who is familiar with how that something works has to say, as you are
doing now. For example, if you were a copier repair technician at one time
and my experience is only with fixing the copiers I've had in my office, I
would probably learn more about troubleshooting a copier by listening to
what you have to say than by arguing that changing the drum will fix a
problem with static buildup. ;-)
[color=blue]
>
> In layman's terms, can you explain why the after CAT sensor can generate
> different codes in entirely different code families? Most codes are
> grouped by family, and there might be failures of a component that can
> appear as different codes within the family, but in this instance there
> are multiple codes that a single component can generate that are not in
> the same code family.[/color]

The OBD II numbering system is determined by the Society of Automotive
Engineers. This site explains the numbering system:
[url]http://www.obdii.com/dtcanatomy.html[/url]

Codes are grouped by system, not by component, and components do not
generate codes. Most sensors are on-off switches like speed sensors; vary
resistance like temperature and pressure sensors and throttle position
sensors; or generate voltage like an O2 sensor. The ECM is programed with
operating parameters for each sensor, so if the voltage is outside of what
the ECM is looking for or the on-off frequency is incorrect or absent, then
the ECM will generate a trouble code for that sensor or component.

[color=blue]
> I come from a troubleshooting background, and have over 20 years in
> various kinds of troubleshooting. Admittedly, my trade experience is not
> automotive, but troubleshooting is troubleshooting until one needs to
> delve relatively deeply into the affected systems. My point is, the
> engineers that I've worked with have a descernable method to their
> collective madness, and having the same component spit out a P0136 or a
> P0420, depending on variables I don't fully understand is a bit confusing.
>[/color]

As you can see from the site I posted above, a P01XX code has to do with
fuel trim (air:fuel mixture), while a P04XX code has to do with secondary
emissions controls. "Secondary" means after combustion has taken place.

The system is very logical if you think simply instead of deeply. Sensors
send a signal, i.e., voltage or frequency, to the ECM. The ECM is
programmed with a bunch of if-then statements. For example, IF the voltage
from bank 1 O2 sensor #2 circuit is less than or equal to .4, THEN
illuminate MIL and store trouble code P0136
[color=blue]
> I'm asking if you can help me get my arms around the variables. I have a
> good grasp of what the codes are telling me, and I'd be looking at the
> same part(s) if either of these two codes came up, but I don't understand
> why the code families are so far removed from one another for what is in
> essence a failure report of the same component. Well, one report says
> (without getting bogged down with detail) the sensor isn't working, the
> other says the part that the sensor is looking at isn't working.
>
>
> BY WAY OF EXAMPLE
> The Evaporative Emissions Control System produces a range of codes that
> are all within a family. A poorly installed gas cap can give a "system
> malfunction" code, a "system gross leak" code, and a "system minor leak"
> code. I concede the point that there can be other problems that give these
> codes, but my point is that all of the problems that I know about relative
> to the system all generate a grouping of codes in the OBD II system.
> Several components within the system give a code that is in the family.
> Relative the CAT, it appears that there is one component that can give a
> code that is in at least two families.
>[/color]

You have to get away from the commonly held notion that a component
generates codes and that code groupings are related to components. Since
the ECM generates codes based on what it expects to see from a sensor, the
proper way to diagnose what caused a particular code is to understand how a
system works and find out what the ECM is expecting to see from a sensor and
then checking the sensor.

Fortunately, most automotive sensors generate voltage, which is relatively
easy to check with a volt meter, or frequency. The proper way to check
frequency is with an ocilloscope, but fortunately, in my experience, a
sensor that generates frequency like a speed sensor or O2 sensor rarely
generates a frequency that is out of spec, and the problem is usually zero
voltage - no frequency, so you can still check with a volt meter.

In the case of conditions that cause the ECM to generate P0420, you have to
understand that while O2 sensor #1 and O2 sensor #2 work the same way, they
serve different purposes. You also have to understand what systems being
monitored are doing and what the signals from O2 sensors mean.

The the voltage from O2 sensor #1 should fluctuate at a frequency a little
greater than 1 cycle per second. If the catalytic converter is working, it
will burn the unburnt and partially burnt fuel in the exhasut gas and even
out the fluctuations in O2 content so the frequency from sensor #2 should be
lower than the frequency from sensor #1. If the frequency from sensor #2 is
the same as sensor #1, the cat is not doing anything so the ECM sets P0420.
In other words, the presence of a signal, not the absence of a signal,
generates P0420.

If it possible for P0420 to come up with a good cat if sensor #1 is not
reacting quickly enough, so its frequency fluctuations are too low and so
the frequency of sensor #2 matches the signal from sensor #1.

In the case of P0136, the ECM does not see any signal from sensor #2 or the
voltage from sensor #2 is too low.
--

Ray O
(correct punctuation to reply)

In article <c18a2$45c6d4c5$47c2b532$23117@msgid.meganewsservers.com>
rokigawaATtristarassociatesDOTcom "Ray O" writes:
[color=blue]
> [...] The proper way to check frequency is with an
> ocilloscope, but fortunately, in my experience, a sensor that
> generates frequency like a speed sensor or O2 sensor rarely
> generates a frequency that is out of spec, and the problem is
> usually zero voltage - no frequency, so you can still check
> with a volt meter.
>
> [...][/color]

Good post, Ray. May I add a caution, when measuring the volts by
a voltmeter? If the voltage is fluctuating and the wave shape is
peculiar, the value shown can be misleading. Imagine a wave that
comprises brief spikes of 1v among a steady 0.1v -- the meter can
not show that accurately, whereas a 'scope would (as you imply).
--
Andrew Stephenson

"Andrew Stephenson" <ames@deltrak.demon.co.uk> wrote in message
news:1170675161snz@deltrak.demon.co.uk...[color=blue]
> In article <c18a2$45c6d4c5$47c2b532$23117@msgid.meganewsservers.com>
> rokigawaATtristarassociatesDOTcom "Ray O" writes:
>[color=green]
>> [...] The proper way to check frequency is with an
>> ocilloscope, but fortunately, in my experience, a sensor that
>> generates frequency like a speed sensor or O2 sensor rarely
>> generates a frequency that is out of spec, and the problem is
>> usually zero voltage - no frequency, so you can still check
>> with a volt meter.
>>
>> [...][/color]
>
> Good post, Ray. May I add a caution, when measuring the volts by
> a voltmeter? If the voltage is fluctuating and the wave shape is
> peculiar, the value shown can be misleading. Imagine a wave that
> comprises brief spikes of 1v among a steady 0.1v -- the meter can
> not show that accurately, whereas a 'scope would (as you imply).
> --
> Andrew Stephenson
>[/color]

Good point. Since I do not have an oscilloscope, I make do with the volt
meter. Fluke makes a very nice meter that has a built-in scope, but I'm
having a hard time justifying its purchase since the $20 Radio Shack meter
purchased about 30 years ago still works.
--

Ray O
(correct punctuation to reply)

"Scott in Florida" <askifyouwant@mindspring.net> wrote in message
news:69tes2lr865h3oktq8235ik98roh1kmf9e@4ax.com...[color=blue]
> On Mon, 5 Feb 2007 11:48:34 -0600, "Ray O"
> <rokigawaATtristarassociatesDOTcom> wrote:
>[color=green]
>>
>>"Andrew Stephenson" <ames@deltrak.demon.co.uk> wrote in message
>>news:1170675161snz@deltrak.demon.co.uk...[/color][/color]

<snipped>
[color=blue][color=green]
>>Good point. Since I do not have an oscilloscope, I make do with the volt
>>meter. Fluke makes a very nice meter that has a built-in scope, but I'm
>>having a hard time justifying its purchase since the $20 Radio Shack meter
>>purchased about 30 years ago still works.[/color]
> Now that is an unacceptable answer!
>
> You mean you can't justify an new toy?
>
> Say it ain't so!!!!!!!!!!!!!!!
>
> --
>
> Scott in Florida
>
>[/color]

I'm saving up for the Aston Martin <g>
--

Ray O
(correct punctuation to reply)

On Mon, 5 Feb 2007 12:35:38 -0600, "Ray O"
<rokigawaATtristarassociatesDOTcom> wrote:
[color=blue]
>
>"Scott in Florida" <askifyouwant@mindspring.net> wrote in message
>news:69tes2lr865h3oktq8235ik98roh1kmf9e@4ax.com...[color=green]
>> On Mon, 5 Feb 2007 11:48:34 -0600, "Ray O"
>> <rokigawaATtristarassociatesDOTcom> wrote:
>>[color=darkred]
>>>
>>>"Andrew Stephenson" <ames@deltrak.demon.co.uk> wrote in message
>>>news:1170675161snz@deltrak.demon.co.uk...[/color][/color]
>
><snipped>
>[color=green][color=darkred]
>>>Good point. Since I do not have an oscilloscope, I make do with the volt
>>>meter. Fluke makes a very nice meter that has a built-in scope, but I'm
>>>having a hard time justifying its purchase since the $20 Radio Shack meter
>>>purchased about 30 years ago still works.[/color]
>> Now that is an unacceptable answer!
>>
>> You mean you can't justify an new toy?
>>
>> Say it ain't so!!!!!!!!!!!!!!!
>>
>> --
>>
>> Scott in Florida
>>
>>[/color]
>
>I'm saving up for the Aston Martin <g>[/color]


Ah ok...then..... <g>

--

Scott in Florida

In article <a2fea$45c77902$44a4a10d$28210@msgid.meganewsservers.com>
rokigawaATtristarassociatesDOTcom "Ray O" writes:
[color=blue]
> "Scott in Florida" <askifyouwant@mindspring.net> wrote in message
> news:69tes2lr865h3oktq8235ik98roh1kmf9e@4ax.com...
>[color=green]
> > [...]
> >
> > You mean you can't justify an new toy?
> >
> > Say it ain't so!!!!!!!!!!!!!!![/color]
>
> I'm saving up for the Aston Martin <g>[/color]

That's a good attitude but, if you want the machine guns behind
the side lights, you're going to have to persuade the licensing
people you have a level-headed outlook. Denying yourself a few
essentials of life on the grounds of mere cost is... not a good
start. Or will you be satisfied with plastic guns and flashing
LEDs, and a grotty sound-maker that goes "budda-budda-budda"?
--
Andrew Stephenson

"Andrew Stephenson" <ames@deltrak.demon.co.uk> wrote in message
news:1170716272snz@deltrak.demon.co.uk...[color=blue]
> In article <a2fea$45c77902$44a4a10d$28210@msgid.meganewsservers.com>
> rokigawaATtristarassociatesDOTcom "Ray O" writes:
>[color=green]
>> "Scott in Florida" <askifyouwant@mindspring.net> wrote in message
>> news:69tes2lr865h3oktq8235ik98roh1kmf9e@4ax.com...
>>[color=darkred]
>> > [...]
>> >
>> > You mean you can't justify an new toy?
>> >
>> > Say it ain't so!!!!!!!!!!!!!!![/color]
>>
>> I'm saving up for the Aston Martin <g>[/color]
>
> That's a good attitude but, if you want the machine guns behind
> the side lights, you're going to have to persuade the licensing
> people you have a level-headed outlook. Denying yourself a few
> essentials of life on the grounds of mere cost is... not a good
> start. Or will you be satisfied with plastic guns and flashing
> LEDs, and a grotty sound-maker that goes "budda-budda-budda"?
> --
> Andrew Stephenson
>[/color]

[Head shaking in disappointment} OK, the machine guns behind the side marker
lights might not be necessary but I would still want the tire shredders <g>
--

Ray O
(correct punctuation to reply)