Is it "normal" for a P0133 (forward oxygen sensor) DTC to clear itself & not return?

[Joe Mastroianni]

The wife got the SES/CEL and two DTCs, both of which were P0133 bank 1
oxygen sensor being slow to respond (one was pending, the other thrown).

She has 135K original miles on this 4cyl 3RZ-FE engine, so I know the
oxygen sensors have never been replaced prior.

Clearly the sensors are due - but the question is WHY/HOW would clearing
the P0133 O2 bank1 sensor1 code cause it NOT to come back?

Is it normal for the OBDII system to be this flaky?

[Kevin Bottorff]

Joe Mastroianni <j...@coohoo.com> wrote in news:kfe3na$kce$1...@dont-email.me:

not real unusual, it will prob come back eventually as the 02 sensor gets
flakier. KB

[Vic Smith]

I've seen it with O2 sensor codes, EGR codes, and misfire codes.
As you say, they come back again if you don't fix the underlying
problem. Just a matter of time and circumstance.
My Lumina 3100 throws an EGR code once a year when I take my vacation
trip. Usually in mountainous territory, but sometimes when I push the
engine at high speed.

[the will]

It isn't that the OBDII system is flaky, it just saw something that
wasn't possda be. Clearing the codes does just that, clears them for
the time being. If the sensor wasn't working at all, the code would
have came back right away. Since it didn't, then at some point in
time, the sensor was "out of it parameters." You can take a scan tool
and watch them work. If there is a problem, the code will reset after
10 or so "drive cycles," might not come back for awhile or even at
all. It/they are probably getting bad so it wouldn't hurt to replace
them.

[jim beam]

some engine computers don't seem to be programmed for mountain descents
with engine braking. a prolonged engine braked descent will trip a
sensor code on an older honda pretty much every time.


--
fact check required

[Kevin McMurtrie]

In article <kfe3na$kce$1...@dont-email.me>,

Every time your engine coughs up oil or soot it slows the sensor down by
covering parts of it. Run the engine hard and it clears up a little.

Changing it now will probably avoid some hassles. A slow sensor can
cause the car to cycle between lean and rich every time the gas pedal is
moved. It makes the car lurch, lag, and generally feel unresponsive.
Those rich to lean cycles will age the catalytic converter more quickly.

The one exception to all of this is a temporary oxygen sensor failure
after an oil change. That means the shop made a big miss and oil fouled
the sensor's outside vent.
--
I will not see posts from Google because I must filter them as spam

[jim beam]

On 02/12/2013 10:32 PM, Kevin McMurtrie wrote:
> In article <kfe3na$kce$1...@dont-email.me>,
> Joe Mastroianni <j...@coohoo.com> wrote:
>
>> The wife got the SES/CEL and two DTCs, both of which were P0133 bank 1
>> oxygen sensor being slow to respond (one was pending, the other thrown).
>>
>> She has 135K original miles on this 4cyl 3RZ-FE engine, so I know the
>> oxygen sensors have never been replaced prior.
>>
>> Clearly the sensors are due - but the question is WHY/HOW would clearing
>> the P0133 O2 bank1 sensor1 code cause it NOT to come back?
>>
>> Is it normal for the OBDII system to be this flaky?
>
> Every time your engine coughs up oil or soot it slows the sensor down by
> covering parts of it. Run the engine hard and it clears up a little.
>
> Changing it now will probably avoid some hassles. A slow sensor can
> cause the car to cycle between lean and rich every time the gas pedal is
> moved.

um, it's constantly cycling anyway as part of normal operations - to
determine the fuel/air bias to achieve stoichiometry. it's got nothing
to do with the pedal being moved.

> It makes the car lurch, lag, and generally feel unresponsive.
> Those rich to lean cycles will age the catalytic converter more quickly.

that's often a sensor temperature problem. cold sensors don't respond
quickly so the engine defaults to its "safe" ratio. that gives poor
performance.

>
> The one exception to all of this is a temporary oxygen sensor failure
> after an oil change. That means the shop made a big miss and oil fouled
> the sensor's outside vent.

it's not exactly a "vent". and it's almost impossible to "foul" in
practice because it relies on solid state diffusion, not air flow. the
diffusion process takes a long time and a thin layer of oil isn't much
of a diffusion barrier, especially not at elevated temperatures.


--
fact check required

[Kevin McMurtrie]

In article <kfmk45$m4$1...@dont-email.me>, jim beam <m...@privacy.net>
wrote:

Yes, it's a diffusion through very tiny gaps, filters, or holes in the
back side of the case. It might even vent into the cable sheeth. It
still temporarily malfunctions when oil burns off of it. Oil smoke and
hot soot does a fine job of consuming oxygen.

Also, the ECU has compensation for a certain O2 sensor delay. When it's
slower than that due to failure, the negative feedback loop becomes a
positive feedback loop for certain frequencies. It causes a bouncing or
lurching feel when moving the gas pedal.

[jim beam]

unless you have some weird sensor from some fringe manufacturer, it
/does/ "vent" into the cable sheath and nowhere else. air "flow" is
measured in molecules - it's absolutely tiny.

> It
> still temporarily malfunctions when oil burns off of it. Oil smoke and
> hot soot does a fine job of consuming oxygen.

i think you have bigger problems if you've burned off the sheath.

>
> Also, the ECU has compensation for a certain O2 sensor delay. When it's
> slower than that due to failure, the negative feedback loop becomes a
> positive feedback loop for certain frequencies. It causes a bouncing or
> lurching feel when moving the gas pedal.

it doesn't have "negative" or "positive" feedback, it has open and
closed loop. if the loop is closed, the computer is able to read a
signal from the sensor and uses it to measure stoichiometry by swinging
the injection between rich and lean and observing the resultant sensor
voltage. it doesn't even try to go into closed loop until the engine
has reached a certain temperature. when it reaches that temperature, it
will try closing the loop based on it's internal map, plus the last
known correction factors. if the sensor isn't responding quickly
enough, the computer ignores readings and stays in open loop [and
typically sets a trouble code]. some fuel injected cars rely solely on
their map and have no feedback loop at all.

bottom line, if you're experiencing lurching, you probably have another
issue that's causing it.


--
fact check required

[Kevin McMurtrie]

In article <kfquoj$dic$1...@dont-email.me>, jim beam <m...@privacy.net>

Closed loop is another term for negative feedback. Delayed negative
feedback is positive feedback for certain frequencies. Stable closed
loops are programmed to compensate for a specific delay in the system.
A large change in delay (shorter or longer) will cause positive feedback
(overshoot, ringing, or full oscillation).

For an example of delayed negative feedback, try balancing a very long
stick vertically on the open palm of your hand. Until you learn to
compensate for delayed visual feedback, you make rapid back and forth
motions that become larger and larger until the stick falls.

[jim beam]

ok, but it's not /called/ "negative" or "positive" feedback for car
oxygen sensors, it's called open and closed loop. an engine can run
just fine in an open loop condition and doesn't become unstable.
indeed, default "safe mode" on encountering a problem is to /go/ open loop.

>
> For an example of delayed negative feedback, try balancing a very long
> stick vertically on the open palm of your hand. Until you learn to
> compensate for delayed visual feedback, you make rapid back and forth
> motions that become larger and larger until the stick falls.
>


--

fact check required

[Joe Mastroianni]

On Mon, 18 Feb 2013 07:34:01 -0800, jim beam wrote:

> ok, but it's not /called/ "negative" or "positive" feedback for car
> oxygen sensors, it's called open and closed loop. an engine can run
> just fine in an open loop condition and doesn't become unstable.
> indeed, default "safe mode" on encountering a problem is to /go/ open
> loop.

Just as a followup - the P0133 hasn't returned yet, and I didn't
do anything other than clear the code. Go figure.

[jgar the jorrible]

Some OBDII systems need to be driven 50 or 60 freeway miles to
actually get all the checks done. City miles don't count. I just
went through this with the bug, and a buddy is currently going through
it with his son's jap car. Found out the hard way by resetting the
computer after a hose detached error, driving it for a month, then
getting smog check notification (which I'm sure I didn't get last
December when I renewed). Had to drive it home on the freeway, then
back the next day to get all checks done - 66 miles each way. Check
engine light came on 5 miles before getting to shop. So I had to get
a new cat. Funny how that happens a year after ten year warranty
expires.

DMV system is even more messed up when the smog rules change. They
sent the old letter from last year when the rules were different, the
shop I liked in the past wasn't certified under the new rules yet.

jg
--
@home.com is bogus.
You really need to check engine when
http://www.nbclosangeles.com/news/local/Jaguar-Burst-into-Flames-in-Mission-Valley-191815951.html

[Joe Mastroianni]

On Tue, 19 Feb 2013 09:09:52 -0800, jgar the jorrible wrote:

> Some OBDII systems need to be driven 50 or 60 freeway miles to actually
> get all the checks done.

It's called the FTP here in California
http://www.arb.ca.gov/msei/onroad/briefs/Publication3.pdf