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Thread: Coded out BST (Battery Safety Terminal) - SRS light and error still on?

  1. #1
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    Coded out BST (Battery Safety Terminal) - SRS light and error still on?

    SOLVED : SRS module was faulty. Replaced it with a used module

    I have an SRS light due to a bad BST.

    Date: 08/31/16 11:45:53
    ECU: MRS4
    JobStatus: OKAY
    Variant: MRS4
    -------------------------------------------------------------
    RESULT: 1 errors in error memory !
    -------------------------------------------------------------
    11 Ignition circuit ZK10 / Safety battery switch 1
    Error frequency : 43
    Error currently present
    Short to ground
    Sporadic error
    ================================================== ===========

    battery.PNG

    I coded the following not active NCS Expert

    BPLUS_TRENNUNG1_1 Battery safety positive terminal aktiv / nicht_aktiv
    BPLUS_TRENNUNG1_2 Battery safety positive terminal aktiv / nicht_aktiv
    BPLUS_TRENNUNG2_1 Battery safety positive terminal aktiv / nicht_aktiv
    BPLUS_TRENNUNG2_2 Battery safety positive terminal aktiv / nicht_aktiv

    1. I disconnected the BST cable to attempt to reset the SRS light - FAIL
    2. I disconnected the battery - FAIL

    Is there something else that needs to be coded out to clear the SRS light?


    Last edited by phamine; 10-27-2017 at 07:00 PM.

  2. #2
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    There appears to be an extra layer of protection on the airbag module that doesnt allow you fully disable certain features. Ive never tried to disable the battery cable, but have experimented with disabling driver airbag for an aftermarket wheel and was unsuccessful.
    Current:

    - 09 335i MSport, FBO.
    - 98 Euro M3, Estoril Blue
    - 04 M3, Carbon Black, 6 Speed Coupe
    - 06 M5, Black on Black, Full Leather.
    - 73 3.0CS, Tagia Green, 5 speed M30b35 converted

    Ex's: 1984 325e, 1988 325IX, 1992 525I, 1995 540i/6, 2002 330i, 2005 330xi, 1992 850i, 2003 330i #1, 2003 330i #2, 2002 330ci, 2004 330ci, 2007 328CI, 2007 335i, 2001 M3, 2006 M5 6 speed

  3. #3
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    You can shove a resistor over the BST squib wires, around 3.3 Ohms, and it'll accept it as fitted.

    Giftschrank Projekt

  4. #4
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    Unfortunately I tried that.

    What I tried to do:
    1. Replace the BST. Though when I check the original one it looked fine. FAIL
    2. I soldered the resistor after the connector in series. FAIL
    3. Soldered a resistor before the connector meaning I cut the connector off thinking it was at fault. FAIL
    4. The last option was to code out the BST itself. FAIL

    Do I have to disconnect a module in the SRS system somewhere and then attempt to reset the light? I'd think coding it out would have worked but it's not. unless I'm missing something.

  5. #5
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    ttt

  6. #6
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    Try finding the wires at the airbag controller, maybe there's damage in the wires somewhere along the line that is triggering it.

    Giftschrank Projekt

  7. #7
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    Going to bump this post. I still haven't been able to resolve this issue.
    I recoded the ABS module to detect the BST to be able to troubleshoot.

    I added a 2.2 ohm resistor inline to from the ABS module to the BST and I still can't clear the error.

    BATTERY SAFETY TERMINAL 1, SHORT CIRCUIT TO NEGATIVE

    What does shirt circuit to negative mean?

    I figure maybe I needed to disconnect and reconnect the ABS module and check it for burnt pins or so - everything looks good.
    Attached Images Attached Images

  8. #8
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    Why not just fix it properly and replace the cable? Seems like youve spent way more effort trying to get around it then to just fix it properly. I pick these cables up at autowreckers for less then $50, and can install the entire thing in about an hour.
    Current:

    - 09 335i MSport, FBO.
    - 98 Euro M3, Estoril Blue
    - 04 M3, Carbon Black, 6 Speed Coupe
    - 06 M5, Black on Black, Full Leather.
    - 73 3.0CS, Tagia Green, 5 speed M30b35 converted

    Ex's: 1984 325e, 1988 325IX, 1992 525I, 1995 540i/6, 2002 330i, 2005 330xi, 1992 850i, 2003 330i #1, 2003 330i #2, 2002 330ci, 2004 330ci, 2007 328CI, 2007 335i, 2001 M3, 2006 M5 6 speed

  9. #9
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    Quote Originally Posted by legoman67 View Post
    Why not just fix it properly and replace the cable? Seems like youve spent way more effort trying to get around it then to just fix it properly. I pick these cables up at autowreckers for less then $50, and can install the entire thing in about an hour.
    That was the first option I took before looking for a work around. It did not work even though the battery bst cable that I tried to replace it with was not blown.

    I just need to understand what short circuit to negative means to be able to diagnose it further.

  10. #10
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    negative = ground. Short to negative means the system is grounding out.
    Current:

    - 09 335i MSport, FBO.
    - 98 Euro M3, Estoril Blue
    - 04 M3, Carbon Black, 6 Speed Coupe
    - 06 M5, Black on Black, Full Leather.
    - 73 3.0CS, Tagia Green, 5 speed M30b35 converted

    Ex's: 1984 325e, 1988 325IX, 1992 525I, 1995 540i/6, 2002 330i, 2005 330xi, 1992 850i, 2003 330i #1, 2003 330i #2, 2002 330ci, 2004 330ci, 2007 328CI, 2007 335i, 2001 M3, 2006 M5 6 speed

  11. #11
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    Unplug the BST and see if you get a code for open circuit.

  12. #12
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    It was the module all along.

    The airbag light is no longer on and there are no active codes. I do see the SRS light intermittently flash on an off.

    I do have to do some reprogramming to the replacement module. It was pulled from a coupe while I have a sedan.
    Attached Images Attached Images

  13. #13
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    We are near each other if you need your module set up right shoot me a pm
    Buy my native installed ISIS ISTA-D/ISTA-P bmw diagnostic laptop. More Info Here!

  14. #14
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    I did this once, just do a ZCS/FA read from the EWS or IKE and write if to the airbag module.

  15. #15
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    I have

    BATTERY SAFETY TERMINAL 1, SHORT CIRCUIT TO POSITIVE (instead of negative as in this post)

    I'm not sure what that means? I thought the BST is already connected to the positive cable of the battery?
    What could be bad, the cable, SRS module or something else?

  16. #16
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    That would be 12v on one of the lines to the BST pyro that go to the SRS module. You could isolate the problem by unplugging the BST and seeing if you get an open circuit code.

  17. #17
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    You mean the little 3 pin yellow connector?
    I disconnected, rescanned, and it's now showing
    Battery satefy terminal 1, resistance too high
    How do I fix this issue?
    I'm not sure how to resolve this short circuit to positive

  18. #18
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    That means that the fault is in the BST itself, to fix that properly you will need to replace the BST.

  19. #19
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    Thanks for the advice.
    I heard there's a repair kit that's only $50 but I wasn't able to find it.
    If anyone is aware, please post the information here.
    I'm trying to find one for M54 (E53)

  20. #20
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    A repair kit does exist (12421733937) though it is much more than $50, you would be best off bypassing it with a resistor or getting a used cable and figuring out how to do a proper butt splice.

  21. #21
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    I think junk yard is the cheapest option by far or buying a used one like this
    https://www.ebay.ca/itm/BMW-E46-3-Se...-127632-2357-0

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