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

On 02/17/2013 07:03 PM, Kevin McMurtrie wrote:
> In article >, jim beam >
> wrote:
>
>> On 02/17/2013 04:34 AM, Kevin McMurtrie wrote:
>>> In article >, jim beam >
>>> wrote:
>>>
>>>> On 02/12/2013 10:32 PM, Kevin McMurtrie wrote:
>>>>> In article >,
>>>>> Joe Mastroianni > 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.
>>>
>>> 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.
>>
>> 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.
>
>
> 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).

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

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.

On Feb 18, 11:53*pm, Joe Mastroianni > wrote:
> 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.

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/lo...191815951.html

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/br...blication3.pdf