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Thread: E46 Apparent Transmission Issue - looking for some help diagnosing

  1. #1
    Join Date
    Jul 2018
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    Boston, MA
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    2003 BMW 325i SportWagon

    E46 Apparent Transmission Issue - looking for some help diagnosing

    I picked up a 2003 325i SportWagon with a 5 speed automatic transmission. This is going to be my kid's "learn to drive" car, so not looking to plow a bunch of money into just in case it doesn't make it through the learning phase. One thing that I am trying to figure out is what may be going on with the transmission. When cruising at about 40mph, with the transmission in 5th gear and while going steady under light load, the engine rpms dip from about 2K to 1,500 and then recovers in a second or so. It will do this repeatedly until there is an acceleration load or need to downshift to maintain speed. I can replicate this going 30mph as well. When I use the manumatic mode, the problem does not occur (or at least it is imperceptible at this point). Any thoughts on what might be going on? I was thinking it might be an issue with the lock-up torque converter, but not sure if this is symptomatic of a different problem as well? Any thoughts would be appreciated. Thanks!

  2. #2
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    Here's a video of the symptom:

    https://youtu.be/uG7cLZuRqJ0

  3. #3
    Join Date
    Dec 2013
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    EXOTICS
    A diagnostic scan of engine and transmission modules for BMW error codes,
    would be your quickest route to correct diagnosis.
    Last edited by MIKYZZ4; 07-23-2018 at 08:07 AM.

  4. #4
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    I scanned for codes and unfortunately it’s coming back with nothing. I wish it had. Given that it won’t replicate in manual mode, I’m wondering if it’s something electronic vs. something slipping. Gonna get under it and poke around this weekend.

  5. #5
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    Not a generic OBD2 scan tool I hope.

  6. #6
    Join Date
    Jul 2018
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    Boston, MA
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    2003 BMW 325i SportWagon
    It’s a deluxe model. Noticed references to some INPA software. Is that a necessary item or a nice to have?
    Last edited by mattm9922; 07-23-2018 at 08:49 AM.

  7. #7
    Join Date
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    EXOTICS
    A scantool that can communicate with all or most BMW modules,
    most importantly the engine(DME) + transmission(EGS) is necessary.

  8. #8
    Join Date
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    2018 BMW M240i
    Please define “deluxe model.” Does it scan the transmission computer (EGS) or not?

  9. #9
    Join Date
    Jul 2018
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    2003 BMW 325i SportWagon
    Actron 9680. It reads transmission codes, but I’m going to further explore it’s capabilities there to understand it’s limitations. Perhaps I need the super deluxe model.

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