check engine light off by itself

I haven't replace the O2 sensor yet and it's now off, it is set to
shut off after a certain days or something else happened?

"Big Blue" <aclaritan@gmail.com> wrote in message
news:fqlum25vqq59nrrbttb8pfgdnertj8q6mc@4ax.com...[color=blue]
>
> I haven't replace the O2 sensor yet and it's now off, it is set to
> shut off after a certain days or something else happened?
>[/color]

I don't know what kind of vehicle you have, but if it is OBD II compliant,
most diagnostic trouble codes have 2-trip fault detection logic. If the
fault is detected for 2 consecutive trips, then the malfunction indicator
light (MIL) is illuminated, and conversely, and if the fault is not detected
on 2 consecutive trips, the MIL light is not illuminated. There are
specific parameters that define a "trip" for each vehicle, like driving at a
certain speeds for a certain amount of time, etc..

Most likely, the condition that was detected is intermittent and is not
always detectable.
--

Ray O
(correct punctuation to reply)

On Thu, 30 Nov 2006 16:27:12 -0600, "Ray O"
<rokigawaATtristarassociatesDOTcom> wrote:
[color=blue]
>
>"Big Blue" <aclaritan@gmail.com> wrote in message
>news:fqlum25vqq59nrrbttb8pfgdnertj8q6mc@4ax.com...[color=green]
>>
>> I haven't replace the O2 sensor yet and it's now off, it is set to
>> shut off after a certain days or something else happened?
>>[/color]
>
>I don't know what kind of vehicle you have, but if it is OBD II compliant,
>most diagnostic trouble codes have 2-trip fault detection logic. If the
>fault is detected for 2 consecutive trips, then the malfunction indicator
>light (MIL) is illuminated, and conversely, and if the fault is not detected
>on 2 consecutive trips, the MIL light is not illuminated. There are
>specific parameters that define a "trip" for each vehicle, like driving at a
>certain speeds for a certain amount of time, etc..
>
>Most likely, the condition that was detected is intermittent and is not
>always detectable.[/color]

2001 Toyota Corolla. Interesting it is on for a few days and now off.
Oh well, I will take your advice and think it "fixed" itself.

"Big Blue" <aclaritan@gmail.com> wrote in message
news:7rkvm25u1d1bj09k5moc9rn5qan2gkin37@4ax.com...[color=blue]
> On Thu, 30 Nov 2006 16:27:12 -0600, "Ray O"
> <rokigawaATtristarassociatesDOTcom> wrote:
>[color=green]
>>
>>"Big Blue" <aclaritan@gmail.com> wrote in message
>>news:fqlum25vqq59nrrbttb8pfgdnertj8q6mc@4ax.com...[color=darkred]
>>>
>>> I haven't replace the O2 sensor yet and it's now off, it is set to
>>> shut off after a certain days or something else happened?
>>>[/color]
>>
>>I don't know what kind of vehicle you have, but if it is OBD II compliant,
>>most diagnostic trouble codes have 2-trip fault detection logic. If the
>>fault is detected for 2 consecutive trips, then the malfunction indicator
>>light (MIL) is illuminated, and conversely, and if the fault is not
>>detected
>>on 2 consecutive trips, the MIL light is not illuminated. There are
>>specific parameters that define a "trip" for each vehicle, like driving at
>>a
>>certain speeds for a certain amount of time, etc..
>>
>>Most likely, the condition that was detected is intermittent and is not
>>always detectable.[/color]
>
> 2001 Toyota Corolla. Interesting it is on for a few days and now off.
> Oh well, I will take your advice and think it "fixed" itself.
>[/color]

All vehicles sold in the U.S. starting with all 1996 model year vehicles are
OBD II compliant; some earlier vehicles are as well. The MIL, A.K.A. check
engine light, will probably come back on with the same trouble codes as the
problem gets worse and more consistent.

I've seen quite a few posts regarding catalytic converters and O2 sensor
problems with that vintage Corolla. Major emissions components like the
catalytic converter (but not O2 sensors) are covered for 8 years or 80,000
miles, whichever comes first, from the date of first use so if your Corolla
falls within that range, I'd take it to a Toyota dealer if the light comes
back on with a converter fault. California and Massachusetts have enhanced
emissions coverage for evaporative emissions control devices so check the
faq section on Toyota's web site if one of those things has a problem.
--

Ray O
(correct punctuation to reply)