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Thread: Pending DTC code on OBD II

  1. #1
    wenmang
    Guest wenmang's Avatar

    Default pending DTC code on OBD II

    Hi,
    I purchased an OBD II scanner, and read a DTC(P0420). When I am reading
    the OBD manual, I don't know what is "pending code", and when and why
    it is there(under what condition it generates a pending code?)? I have
    cleared the DTC, but manual mentions that OBD 2 Drive cycle must be
    performed before resetting all the monitors, what is "OBD 2 Drive
    cycle"? If I just drive my car after clearing DTC, will the car do "OBD
    2 Drive cycle" automatically?
    Thanks.
    WM

  2. #2
    wenmang
    Guest wenmang's Avatar

    Default pending DTC code on OBD II

    The website doesn't have search functionality, I found info about
    "drive cycle", but I cannot find about "generating pending code".
    Hopefully, this can be answered here. Thanks.

  3. #3
    wenmang
    Guest wenmang's Avatar

    Default pending DTC code on OBD II

    Thanks Ray. I asked about P0420 before. I just want to understand why
    OBD II manual indicates that how OBD II scanner can detect a pending
    DTC and what does it mean? like potential problem on the way if it
    presents or some kind of alert functionality.
    Thanks.

  4. #4
    wenmang
    Guest wenmang's Avatar

    Default pending DTC code on OBD II

    Got answer from manufacture, thanks.
    "The tool will display pending codes. A pending code is a problem that
    the vehicle's computer has seen, but has not seen it enough to consider
    it a priority and turn on the MIL. "

  5. #5
    wenmang
    Guest wenmang's Avatar

    Default pending DTC code on OBD II

    That is why I am aksing when the yellow LED is on, what does it mean?

  6. #6
    wenmang
    Guest wenmang's Avatar

    Default pending DTC code on OBD II

    Thanks Ray. Actually I spent $69 on OBD 2, they have two models, the
    other one costs $100 at walmart. They are not the one advertised on
    their website.

  7. #7
    Gord Beaman
    Guest Gord Beaman's Avatar

    Default pending DTC code on OBD II

    "Ray O" <rokigawa@tristarassociatesDOT.com> wrote:

    >
    ><wenmang..........m> wrote in message
    >news:1130353018.188342.325610@o13g2000cwo.googleg ro...........
    >> Thanks Ray. I asked about P0420 before. I just want to understand why
    >> OBD II manual indicates that how OBD II scanner can detect a pending
    >> DTC and what does it mean? like potential problem on the way if it
    >> presents or some kind of alert functionality.
    >> Thanks.
    >>

    >
    >The OBD II system does not detect or predict pending problems. It can only
    >detect the presence or absence of problems.
    >
    >To reduce false alarms, some problems need to be detected over the course of
    >several trips before the check engine light (formally called a malfunction
    >indicator light, or MIL) is illuminated and needs to not detect the problem
    >of the course of several trips to extinguish the MIL. Toyota calls this 2
    >trip detection logic,


    snip

    But Ray, isn't that the same thing as predicting?...if it saw the
    same error several times in a row then it'll turn on the MIL,
    right?...so if it saw the same error maybe twice, then no error
    for another several trips then three more in a row...see my
    point?...isn't it 'predicting' a problem (sort of?)
    --

    -Gord.
    (use gordon in email)

  8. #8
    Gord Beaman
    Guest Gord Beaman's Avatar

    Default pending DTC code on OBD II

    "Ray O" <rokigawa@tristarassociatesDOT.com> wrote:

    >
    >"Gord Beaman" <gord@islandtelecom.com> wrote in message
    >newsd80m1h3cc1aep9duuqbvbus1elk7cqgan@...........
    >> "Ray O" <rokigawa@tristarassociatesDOT.com> wrote:
    >>
    >>>
    >>><wenmang..........m> wrote in message
    >>>news:1130353018.188342.325610@o13g2000cwo.googl egro...........
    >>>> Thanks Ray. I asked about P0420 before. I just want to understand why
    >>>> OBD II manual indicates that how OBD II scanner can detect a pending
    >>>> DTC and what does it mean? like potential problem on the way if it
    >>>> presents or some kind of alert functionality.
    >>>> Thanks.
    >>>>
    >>>
    >>>The OBD II system does not detect or predict pending problems. It can
    >>>only
    >>>detect the presence or absence of problems.
    >>>
    >>>To reduce false alarms, some problems need to be detected over the course
    >>>of
    >>>several trips before the check engine light (formally called a malfunction
    >>>indicator light, or MIL) is illuminated and needs to not detect the
    >>>problem
    >>>of the course of several trips to extinguish the MIL. Toyota calls this 2
    >>>trip detection logic,

    >>
    >> snip
    >>
    >> But Ray, isn't that the same thing as predicting?...if it saw the
    >> same error several times in a row then it'll turn on the MIL,
    >> right?...so if it saw the same error maybe twice, then no error
    >> for another several trips then three more in a row...see my
    >> point?...isn't it 'predicting' a problem (sort of?)
    >> --
    >>
    >> -Gord.
    >> (use gordon in email)

    >
    >I guess it's a matter of semantics. I was thinking of "predicting" as
    >anticipating a problem before the problem actually occurs, and I was
    >thinking of the 2 trip detection logic as double-checking.
    >
    >On trouble codes that have 2 trip detection logic, I guess you could
    >consider a problem with one trip, and the second trip has not occurred yet a
    >"prediction" but that assumes that the problem will definitely occur on
    >another trip. I gather that the OP's scan tool will illuminate a light
    >showing that the ECU has stored a trouble code for 1 trip but not another
    >trip yet so the MIL is not illuminated. The problem is, you normally would
    >not scan for codes unless the MIL comes on, so unless you drive around with
    >the scan tool connected, there is little benefit to "predicting" a trouble
    >code.


    Of course, right you are sir, thanks...
    --

    -Gord.
    (use gordon in email)

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