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Thread: U1016

  1. #21
    Lifetime Member mr.prick's Avatar
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    LOL
    either way i have a problem with the "class 2 serial communications".
    this happened 2 other times but i got it going after recharging the battery,
    i think it`s from all the power i pull through the car. (inverter, stereo, extra sensors)
    i took off the rubber boots on the +/- cable of the battery and they looked fine.
    i even check the ground above the starter.
    LOL
    whats the easiest way to find an open circuit through miles of wire.

  2. #22
    Joe (Moderator) joecar's Avatar
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    Disconnect all modules from the class 2 bus, and probe the bus for shorts/opens.

    Not having power/ground to all modules can cause disruption on the bus, as can a module that won't stop chatting on the bus (for some reason it is trying to complain about something), as can some shorts, as can pulling too much power.

    To find an open in a power circuit:
    - connect DMM - to battery negative;
    - using DMM + probe power circuit, starting closest to battery:
    --> if DMM shows exact battery voltage, then open is downstream (away from battery);
    --> if DMM shows a slight drop, continue probing downstream;
    --> if DMM shows a large drop or floating, then you have just passed the open.

    To find an open in a ground circuit:
    - connect DMM + to battery positive;
    - using DMM - probe ground circuit, starting closest to battery:
    --> if DMM shows exact battery voltage, then open is downstream (away from battery);
    --> if DMM shows a slight drop, continue probing downstream;
    --> if DMM shows a large drop or floating, then you have just passed the open.

    Even if a connection looks good, probe either side of it...
    Also spraying it with a small amount of WD40 will internally clean it up.


    I don't like using the cigar lighter to power the scantool because doing this can set up a ground loop...

    a ground loop is when to "grounds" which are at different potentials wrt to each other are connected... the current that flows between them is the difference between their potentials divided by the resistance of the connection, and often this current can be large and can fry something.

  3. #23
    Lifetime Member mr.prick's Avatar
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    Quote Originally Posted by joecar View Post
    a ground loop is when to "grounds" which are at different potentials wrt to each other are connected... the current that flows between them is the difference between their potentials divided by the resistance of the connection, and often this current can be large and can fry something.
    this is what i am thinking.
    i also might change the ground wires for the hell of it. (big3)
    then what to do when/if i find a bad wire.
    i guess it will be like eating spaghetti.
    thanks
    Last edited by mr.prick; September 5th, 2008 at 02:25 PM.

  4. #24
    Lifetime Member mr.prick's Avatar
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    if i am doing this right,
    the star has no voltage unhooked and 1.__ resistance at each pin.
    i get 12 volts from the main fuse box and 1.__ resistance.
    does this mean i have a bad ground/hot wire at the battery?

  5. #25
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by mr.prick View Post
    if i am doing this right,
    the star has no voltage unhooked and 1.__ resistance at each pin.
    i get 12 volts from the main fuse box and 1.__ resistance.
    does this mean i have a bad ground/hot wire at the battery?
    By star are you referring to the class 2 bus...?

    Which wires are you ohming wrt which other wires...?

    The DMM displays 1.___ for overrange (manual range) or for open-circuit/high-resistance (auto range)... are you set on auto range...?

    Where do you see open circuit...?

    Which circuit diagram are you looking at...?

    Remember to not ohm a live circuit.

  6. #26
    Lifetime Member mr.prick's Avatar
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    i am checking each module`s wire to the star bus now.
    i don`t think i was doing it right before.
    PCM
    blue 58 to STAR C - audible
    blue 58 to OBDII pin 2 - audible
    blue 57 to positive battery cable - audible

    SDM (air bag)
    SDM connector (dark blue wire) to STAR E - audible

    EBCM
    EBCM pin 25 (light blue) to STAR J - audible
    Last edited by mr.prick; September 7th, 2008 at 12:20 PM.

  7. #27
    Lifetime Member mr.prick's Avatar
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    does anyone know where pin J meets the IPC?
    or any reason connection cannot be made through OBDII port?

  8. #28
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by mr.prick View Post
    does anyone know where pin J meets the IPC?
    or any reason connection cannot be made through OBDII port?
    See the attached diagrams(look where splice pack SP200 connects to the module).
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  9. #29
    Joe (Moderator) joecar's Avatar
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    I think your serial bus is ok... problem may be ground related or a bad module on the bus.

  10. #30
    Lifetime Member mr.prick's Avatar
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    Quote Originally Posted by joecar View Post
    I think your serial bus is ok... problem may be ground related or a bad module on the bus.
    thanks for the IPC schematic.

    is the BCM part of the IPC?


    do you mean a ground to one of the modules?

    from what little i`ve seen on something like this has been,
    a possible open on the bus or a failed module.
    i don`t think bad ground anywhere other than whats on the bus would do this.

    i am checking the bus first then moving on.
    all the grounds i have checked go all the way back to the
    battery cable end.

    here`s what i recall checking so far
    PCM
    blue 58 to STAR C - audible
    blue 58 to OBDII pin 2 - audible
    blue 57 to positive battery cable - audible
    red 1 to negative battery cable - audible
    red 40 to negative battery cable - audible

    SDM (air bag) connector (dark blue wire) to STAR E - audible

    EBCM pin 25 (light blue) to STAR J - audible

    BCM to battery (+/-) - audible

    cig lighter (+/-) - audible

    DLC
    DLC 4 to negative battery cable - audible
    DLC 5 to negative battery cable - audible

    IPC to (gray) STAR L - audible
    Last edited by mr.prick; September 8th, 2008 at 12:15 PM.

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