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Thread: Converting 95 M3 OBD1 to OBD2

  1. #1
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    Converting 95 M3 OBD1 to OBD2

    I have some silly questions when it comes to converting an OBD1 car to OBD2 (engine harness side anyways). It seems most of the research I have found are from people going from an OBD2 S52 converting it to OBD1. I did watch RK Tunes video on the subject and it was very informative.

    My question: my 95 M3 has one plug X20 (I assume) and I know the OBD2 cars have 3 connectors. The small one in the middle for traction control I believe which will not be needed, but what is the other one for? Is it needed? Do people cut those out of the OBD2 harness or have them laying by the fusebox? Is there any benefit getting a 96 harness without the traction control?

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    I did an OBD2 swap in a 1994 325i chassis, and never found a how-to, so after I searched I went to the ETM's(http://wedophones.com/Manuals/BMW/) for both cars. You have to move a couple of wires to different pins inside of the X20 and move a few wires into the X20 connector, all on the engine harness side. You will need to add a circuit to the X20 chassis side, needed if using all 4 O2 sensors. I deleted all of the SAP system wires(even the vacuum solenoid connector that comes out of the fuel injector plastic), Fuel tank pressure sensor, and running losses(independent wire that runs to the fuel filter area). I also wired in an ODB2 connector but put it under the glove box to free up any wires from being around the drivers feet.


    http://www.bimmerforums.com/forum/sh...o-OBD1-Chassis
    Last edited by AJLM34A; 05-06-2022 at 07:34 PM.
    [IMG][/IMG]

  3. #3
    RRSperry's Avatar
    RRSperry is offline Senior Moment Member BMW E36 M3 Expert
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    Just asking, but why?
    No matter where you go, there you are...

  4. #4
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    Quote Originally Posted by RRSperry View Post
    Just asking, but why?
    Because OBD1 is awful when things are not working and OBD2 tuning is superior.

  5. #5
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    Quote Originally Posted by RRSperry View Post
    Just asking, but why?
    turbo car running Miller WAR chip and haven't been able to get it dialed in. Most of my friends are running obd2 and love their setup so was hoping to make the switch. May just buy RK Tunes obd1 tuning package whenever it goes on sale, but exploring my options at the moment

  6. #6
    RRSperry's Avatar
    RRSperry is offline Senior Moment Member BMW E36 M3 Expert
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    Well, I'd think that you'd have to replace the entire engine wiring harness, including installing the OBD2 port, ECU and gauge cluster, and then recode or eliminate the EWS. I'm sure you can do it, I mean BMW did it..
    No matter where you go, there you are...

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    Ya why

  8. #8
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    the plan is to have the obd2 engine harness hooked up to the obd1 body harness and fully functioning. need to source as obd2 wiring harness, but have all the obd2 sensors for the engine and obd2 ecu. Tuner will delete ews when it is tuned and an obd2 cluster is not needed.

    my main hang up is on the x20 connector and what’s needed there

  9. #9
    NeilM is offline Member BMW E36 M3 Expert
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    Quote Originally Posted by lbennyboobool View Post
    my main hang up is on the x20 connector and what’s needed there
    Time for a trip to the wiring diagrams in the Bentley manual. But you're still swimming upstream.

    Neil
    96 M3 — native born OBD2

  10. #10
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    Quote Originally Posted by lbennyboobool View Post
    the plan is to have the obd2 engine harness hooked up to the obd1 body harness and fully functioning. need to source as obd2 wiring harness, but have all the obd2 sensors for the engine and obd2 ecu. Tuner will delete ews when it is tuned and an obd2 cluster is not needed.

    my main hang up is on the x20 connector and what’s needed there
    EWS maybe? I stayed with OBD1 for my s52 swap, the X20 connector was modified to override EWS aka clipping a big green wire.

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    Quote Originally Posted by Braymond141 View Post
    Because OBD1 is awful when things are not working and OBD2 tuning is superior.
    Not true, the Bosch 3.3.1 system actually makes more power and has more aggressive maps than Siemens 41.2. Also Bosch 3.3.1 has a very good diagnostic support trough INPA.

  12. #12
    NeilM is offline Member BMW E36 M3 Expert
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    Quote Originally Posted by hakentt View Post
    Also Bosch 3.3.1 has a very good diagnostic support trough INPA.
    INPA, however, is a black hole of obscurity.

  13. #13
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    Quote Originally Posted by hakentt View Post
    very good diagnostic support trough INPA.
    No.

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