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Thread: 1995 E34 Problem Connecting to the CAN Bus

  1. #1
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    1995 E34 Problem Connecting to the CAN Bus

    Hello and thank you for reading,
    I have a 1995 540i MSport Automatic. I have had two shops try to connect their scanners to my car inn order to reset my SRS light and to install a Dinan chip. One shop tried 3 different diagnostic scanners and in all cases he got an error "unable to connect" or something like that.

  2. #2
    moroza's Avatar
    moroza is offline MORΩN ΛABIA BMW CCA Member
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  3. #3
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    Actually there is a CAN Bus. Been on BMW's even prior to my 1995. As I understand it was developed in 1983 at Robert Bosch. The DME, trans controller, EWS II, ABS and On-Board controller are all connected via a twisted pair. Yes my car has the 20 pin connector but what ever diagnostic tool is plugged in to it communicates to all the controller via the bus

  4. #4
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    Seems like you already know what you're talking about. Us brainlets don't have E34s with a CANBUS, so we can't help you. Maybe keep trying different scanners? One will surely pick it up eventually.

  5. #5
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    Quote Originally Posted by Creesic View Post
    Seems like you already know what you're talking about. Us brainlets don't have E34s with a CANBUS, so we can't help you. Maybe keep trying different scanners? One will surely pick it up eventually.
    Any information i have is what I am able to glean from sites such as this one. The gentleman that told me to educate myself on CAN was from a Dinan dealer in southern california. He is the one who tried tree different scanners all of which gave him the same unable to connect error. I dont feel like taking my car to a shop on a time and material basis and spend thousands of dollars when i could troubleshoot or fix the problem myself if i am able to find correct information. So if a bus is a physical thing maybe we are talking semantics. What I do know is that there is a twisted pair of wires used for network communication between controllers. What I dont know is what controllers must be present for the system to work and what controllers could be causing the problem and additionally how to diagnose a faulty controller. Everything on the car works fine and no check engine light. The only light that is on is the SRS and its on because i screwed up and turned on the ignition without the drivers side airbag pluged in

  6. #6
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    Shogun's SRS reset tool worked on resetting the SRS light on my 95 530. I used a manual process to reset the SRS light on my 89 535.
    demet

  7. #7
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    Quote Originally Posted by demetk View Post
    Shogun's SRS reset tool worked on resetting the SRS light on my 95 530. I used a manual process to reset the SRS light on my 89 535.
    I have a oil service and inspection reset tool which will not reset the inspection most likely because of the CAN communication problem I am facing at the moment. Just reseting the SRS is only part of the problem the other part is not being able to connect to CAN for other diagnostic issues which may arise in the future

  8. #8
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    E34 needs ADS cable to properly read data. Scanners may just not support old K-Line format. With ADS and DIS I can read all modules in my 94 525i

  9. #9
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    Quote Originally Posted by katit2 View Post
    E34 needs ADS cable to properly read data. Scanners may just not support old K-Line format. With ADS and DIS I can read all modules in my 94 525i
    Thank you, I will check that out but I'm sure i will still encounter my communications problem

  10. #10
    moroza's Avatar
    moroza is offline MORΩN ΛABIA BMW CCA Member
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    I was under the impression that CANBUS was a much more heavily-wired affair than the two-wire "Data Link"?

  11. #11
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    Quote Originally Posted by moroza View Post
    I was under the impression that CANBUS was a much more heavily-wired affair than the two-wire "Data Link"?
    No idea if there is a canbus, but a two-wire "Data Link" is precisely the point if there is one. multiplexing info on a single pair is what a canbus system is supposed to do (think adsl modem on 2 wire phone line etc, connecting everything you want access too - rather than dedicated wires to every unique address in the outside world for every single thing you want access to).

    I'd settle for a working engine check light in my older 525. Without it I feel like I don't even have OBD1, more like OBD0
    Last edited by fo3; 05-17-2018 at 05:35 PM.

  12. #12
    moroza's Avatar
    moroza is offline MORΩN ΛABIA BMW CCA Member
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    Ok, I learned something. I think my assumption came from having worked as a PC tech ages ago, never owned an OBD2 car, and done some electrical work on newer Volvos that make M70 wiring look like a Model T in comparison...

  13. #13
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    Hello,

    Seems like everyone has already helped with the diag part. Just wanted to throw out there that I help run an E34 M Sport registry on Facebook. Join up if you haven't already.
    https://www.facebook.com/groups/E34Msport/

    Thank you,

    Justin

    95 540i6 M Sport - 95 525it S52/OBD2 - 433k E36 328i5 - X5D that hit a pothole - IG: @justinmurray95

  14. #14
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    There is no CAN bus on E34, the communication is done via 2 wire and it's a serial communication ADS (modified rs232).

    I use to connect to mine with i-diag + 20pin adapter, the autoscan function doesn't work, it need to be selected manually each module.

    List of modules:

    SRS.png EGS.png ABS.png DWA.png DME.png

  15. #15
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    Quote Originally Posted by daven540i View Post
    Actually there is a CAN Bus. Been on BMW's even prior to my 1995. As I understand it was developed in 1983 at Robert Bosch. The DME, trans controller, EWS II, ABS and On-Board controller are all connected via a twisted pair. Yes my car has the 20 pin connector but what ever diagnostic tool is plugged in to it communicates to all the controller via the bus
    e34 95 and older don't have a canbus, they have a d-bus

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