check engine light-question.

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Old 03 Mar 2005, 12:12 pm   #1 (permalink)
Big Kahuna
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Default check engine light-question.

OK,

I had the check engine light come on in my 02 with 20k miles. The Camry
is under warranty, so I took her to the dealer. The diagnostic showed
two parts bad (MAF and AF sensors). They replaced one and had to order
the other one. But here's the odd thing:

When they replaced the MAF (Mass Air Flow) sensor, they told me the
other one was on order but when I drove away, ***the check engine light
was out and never came back on***.

About 10 days later, the part came in and I returned to the dealer to
have the second sensor installed. When I looked at the ticket after
getting the car back, it said "confirmed code (something or other) air
flow sensor with diagnostic tool. Replaced AF sensor. Checked again
with diagnostic tool and error code cleared."

OK. But if that AF sensor was indeed "bad"--why wasn't the "check
engine" light on during the 10 days I was waiting for the part? In
other words, if the diag tool can confirm that it was bad, why wasn't
the check engine light on?

The scary thing is that I'm afraid that they somehow disabled the check
engine light while waiting for the part--then never turned it back on.
Could that be the case?
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Old 03 Mar 2005, 01:16 pm   #2 (permalink)
Travis Jordan
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Default Re: check engine light-question.

Big Kahuna wrote:
> I had the check engine light come on in my 02 with 20k miles. The
> Camry is under warranty, so I took her to the dealer. The diagnostic
> showed two parts bad (MAF and AF sensors). They replaced one and had
> to order the other one. But here's the odd thing:


Most likely the diagnostic meant "MAF OR AF sensor", not "MAF AND AF
sensor". Your dealer is a parts changer, not a diagnostician. Tell 'em
you don't need the back ordered part.


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Old 03 Mar 2005, 02:01 pm   #3 (permalink)
Big Kahuna
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Default Re: check engine light-question.

In article <ZnJVd.152429$Zm5.20169@news.easynews.com>,
"Travis Jordan" <no.one@no.net> wrote:

> Big Kahuna wrote:
> > I had the check engine light come on in my 02 with 20k miles. The
> > Camry is under warranty, so I took her to the dealer. The diagnostic
> > showed two parts bad (MAF and AF sensors). They replaced one and had
> > to order the other one. But here's the odd thing:

>
> Most likely the diagnostic meant "MAF OR AF sensor", not "MAF AND AF
> sensor". Your dealer is a parts changer, not a diagnostician. Tell 'em
> you don't need the back ordered part.


I guess I wasn't clear. Two codes appeared when I first took it in
indicating two bad sensors. The had one part in stock, they ordered the
other one. Both have *already* been installed. So the "and/or" bit is
moot.

The question is: Why didn't the "check engine" light appear during the
time I was waiting for the second sensor part to arrive if it was bad?
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Old 03 Mar 2005, 02:12 pm   #4 (permalink)
Travis Jordan
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Default Re: check engine light-question.

Big Kahuna wrote:
> I guess I wasn't clear. Two codes appeared when I first took it in
> indicating two bad sensors. The had one part in stock, they ordered
> the other one. Both have *already* been installed. So the "and/or"
> bit is moot.
>
> The question is: Why didn't the "check engine" light appear during
> the time I was waiting for the second sensor part to arrive if it was
> bad?


The answer should be obvious: it wasn't.

What is the probability that both these parts would fail in the same
day? Almost zero, I would say.


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Old 03 Mar 2005, 02:29 pm   #5 (permalink)
Philip
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Default Re: check engine light-question.

Big Kahuna wrote:
> OK,
>
> I had the check engine light come on in my 02 with 20k miles. The
> Camry is under warranty, so I took her to the dealer. The diagnostic
> showed two parts bad (MAF and AF sensors). They replaced one and had
> to order the other one. But here's the odd thing:
>
> When they replaced the MAF (Mass Air Flow) sensor, they told me the
> other one was on order but when I drove away, ***the check engine
> light was out and never came back on***.
>
> About 10 days later, the part came in and I returned to the dealer to
> have the second sensor installed. When I looked at the ticket after
> getting the car back, it said "confirmed code (something or other) air
> flow sensor with diagnostic tool. Replaced AF sensor. Checked again
> with diagnostic tool and error code cleared."
>
> OK. But if that AF sensor was indeed "bad"--why wasn't the "check
> engine" light on during the 10 days I was waiting for the part? In
> other words, if the diag tool can confirm that it was bad, why wasn't
> the check engine light on?
>
> The scary thing is that I'm afraid that they somehow disabled the
> check engine light while waiting for the part--then never turned it
> back on. Could that be the case?


You Check Engine light turns ON when you turn the key to ON. It goes out
after the engine starts. Is this the way yours behaves?
--

- Philip



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Old 03 Mar 2005, 02:29 pm   #6 (permalink)
Philip
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Default Re: check engine light-question.

Big Kahuna wrote:
> In article <ZnJVd.152429$Zm5.20169@news.easynews.com>,
> "Travis Jordan" <no.one@no.net> wrote:
>
>> Big Kahuna wrote:
>>> I had the check engine light come on in my 02 with 20k miles. The
>>> Camry is under warranty, so I took her to the dealer. The
>>> diagnostic showed two parts bad (MAF and AF sensors). They
>>> replaced one and had to order the other one. But here's the odd
>>> thing:

>>
>> Most likely the diagnostic meant "MAF OR AF sensor", not "MAF AND AF
>> sensor". Your dealer is a parts changer, not a diagnostician. Tell
>> 'em you don't need the back ordered part.

>
> I guess I wasn't clear. Two codes appeared when I first took it in
> indicating two bad sensors. The had one part in stock, they ordered
> the other one. Both have *already* been installed. So the "and/or"
> bit is moot.
>
> The question is: Why didn't the "check engine" light appear during
> the time I was waiting for the second sensor part to arrive if it was
> bad?


If the MIL (Check Engine) light stays out, then cancel the replacement of
the other part.
--

- Philip



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Old 03 Mar 2005, 02:29 pm   #7 (permalink)
Philip
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Default Re: check engine light-question.

Travis Jordan wrote:
> Big Kahuna wrote:
>> I guess I wasn't clear. Two codes appeared when I first took it in
>> indicating two bad sensors. The had one part in stock, they ordered
>> the other one. Both have *already* been installed. So the "and/or"
>> bit is moot.
>>
>> The question is: Why didn't the "check engine" light appear during
>> the time I was waiting for the second sensor part to arrive if it was
>> bad?

>
> The answer should be obvious: it wasn't.
>
> What is the probability that both these parts would fail in the same
> day? Almost zero, I would say.


Depends if the owner was monkeying around things under the hood, IE, pulling
plugs or vacuum lines from those sensors while the engine was running. Or,
by installing one of those K/N air filters that let oil and grit contaminate
the Air Flow sensor.
--

- Philip



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Old 03 Mar 2005, 04:41 pm   #8 (permalink)
davidj92
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Default Re: check engine light-question.

Big Kahuna wrote:
> OK,
>
> I had the check engine light come on in my 02 with 20k miles. The
> Camry is under warranty, so I took her to the dealer. The diagnostic
> showed two parts bad (MAF and AF sensors). They replaced one and had
> to order the other one. But here's the odd thing:
>
> When they replaced the MAF (Mass Air Flow) sensor, they told me the
> other one was on order but when I drove away, ***the check engine
> light was out and never came back on***.
>
> About 10 days later, the part came in and I returned to the dealer to
> have the second sensor installed. When I looked at the ticket after
> getting the car back, it said "confirmed code (something or other) air
> flow sensor with diagnostic tool. Replaced AF sensor. Checked again
> with diagnostic tool and error code cleared."
>
> OK. But if that AF sensor was indeed "bad"--why wasn't the "check
> engine" light on during the 10 days I was waiting for the part? In
> other words, if the diag tool can confirm that it was bad, why wasn't
> the check engine light on?
>
> The scary thing is that I'm afraid that they somehow disabled the
> check engine light while waiting for the part--then never turned it
> back on. Could that be the case?


I'll stand to be corrected but I think the MAF sensor is a critical feedback
and will set the CEL while the AF sensor is not and won't set a CEL.
davidj92


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Old 03 Mar 2005, 04:42 pm   #9 (permalink)
Wulfdog
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Default Re: check engine light-question.

I wonder about that too. I had a pickup that I drove through a mud hole.
The ABS light came on while it was still under warrenty I kept taking it
back to the dealership and making them try to get the light to stop coming
on. After about the third time the light stopped coming on. And since 1995
it has never came on again ever. You tell me, did they fix it or unplug it?
I'd say the latter. We also took a bus into a repair shop to have them
figure out why the check engine light was always on. It went out after they
were through with it, but after examining the dash in the sunlight, there
was black tape over the check engine light. When we peeled the tape off,
the light was still on under it. We took it back and made them send it to
the factory to fix it. I told them they didn't even want to know what our
lawyers would do to them for trying the shit on us.

John

"Big Kahuna" <none@nothanks.com> wrote in message
news:none-6C25FD.10120203032005@news.stanford.edu...
> OK,
>
> I had the check engine light come on in my 02 with 20k miles. The Camry
> is under warranty, so I took her to the dealer. The diagnostic showed
> two parts bad (MAF and AF sensors). They replaced one and had to order
> the other one. But here's the odd thing:
>
> When they replaced the MAF (Mass Air Flow) sensor, they told me the
> other one was on order but when I drove away, ***the check engine light
> was out and never came back on***.
>
> About 10 days later, the part came in and I returned to the dealer to
> have the second sensor installed. When I looked at the ticket after
> getting the car back, it said "confirmed code (something or other) air
> flow sensor with diagnostic tool. Replaced AF sensor. Checked again
> with diagnostic tool and error code cleared."
>
> OK. But if that AF sensor was indeed "bad"--why wasn't the "check
> engine" light on during the 10 days I was waiting for the part? In
> other words, if the diag tool can confirm that it was bad, why wasn't
> the check engine light on?
>
> The scary thing is that I'm afraid that they somehow disabled the check
> engine light while waiting for the part--then never turned it back on.
> Could that be the case?



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Old 04 Mar 2005, 10:04 am   #10 (permalink)
Philip
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Default Re: check engine light-question.

davidj92 wrote:
> Big Kahuna wrote:
>> OK,
>>
>> I had the check engine light come on in my 02 with 20k miles. The
>> Camry is under warranty, so I took her to the dealer. The diagnostic
>> showed two parts bad (MAF and AF sensors). They replaced one and had
>> to order the other one. But here's the odd thing:
>>
>> When they replaced the MAF (Mass Air Flow) sensor, they told me the
>> other one was on order but when I drove away, ***the check engine
>> light was out and never came back on***.
>>
>> About 10 days later, the part came in and I returned to the dealer to
>> have the second sensor installed. When I looked at the ticket after
>> getting the car back, it said "confirmed code (something or other)
>> air flow sensor with diagnostic tool. Replaced AF sensor. Checked
>> again with diagnostic tool and error code cleared."
>>
>> OK. But if that AF sensor was indeed "bad"--why wasn't the "check
>> engine" light on during the 10 days I was waiting for the part? In
>> other words, if the diag tool can confirm that it was bad, why wasn't
>> the check engine light on?
>>
>> The scary thing is that I'm afraid that they somehow disabled the
>> check engine light while waiting for the part--then never turned it
>> back on. Could that be the case?

>
> I'll stand to be corrected but I think the MAF sensor is a critical
> feedback and will set the CEL while the AF sensor is not and won't
> set a CEL. david


Probably a good idea for discussion is to be clear about what these alphabet
descriptions really mean. MassAirFlow (MAF) sensor is checked by the
ElectronicControlUnit (ECU). An AirFlow sensor is functionally the same
thing. The ECU will flash the CEL with the failure of any air flow
measuring device or ManifoldAirPressure (MAP) sensor. (yes there are a
bunch of other sensors not mentioned that are monitored by the ECU).
--

- Philip



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