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m52b28 325e swap electrical/ecu questions/recommendations

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    m52b28 325e swap electrical/ecu questions/recommendations

    Finally dropping my m52 into my 325e this weekend. I am wondering about flashing my ECU..

    When i send it out to for the ews to be flashed, should i have all the mods i want done to the motor finished prior and everything tuned at once? I plan on doing the m50 manifold swap, as well as adding my s50 cams and s52 crank to it. I plan on coming back to the cams and crank after i get the m52 in and running but if its best to have it all done prior and just flashing/tuning it once then i will postpone the swap.

    Recommendations on who to go to for the ecu flash/tune would be appreciated as well.

    I am looking for a wiring diagram for the 325e as well. I find a lot of information about the c101 connector but i do not have that connector in my 85 325e. Garagistic sells the plug and play adapter for the c101 but not for the 325e connector so i will be stuck wiring it myself. Im trying to get rid of as much wiring as i can in my chassis harness and my m52 harness.

    Any guidance or points of reference for more research is greatly appreciated. Any recommendations in any of the steps of the swap as well. Thanks
    Last edited by Yayrea; 08-27-2019, 07:15 PM.

    Pmd Sir


      So i have the rectangle/square 19 pin connector on the 85 325e. Do i want to buy both sides of the round c101 connector; one for the chassis side, and one for the m52? or just the chassis side?


        Diagram for Square Connector and C101 Connector.

        You need one side of the 101 connector. The Female if I remember correctly, that will replace the square connector and you can splice the proper wires using the diagram.

        Assuming your running OBD II you will need to delete EWS, SAP, and EGR. and Plug the ports in the exhaust manifold.

        then there are a few wires in the glove box you will have to run to.
        I traced the C104 wires back to the cluster and tapped into the tach wire (black) there, ran a wire to appropriate pin of the E36 harness

        Same as the tach but it's the yellow/white wire

        The DME uses a switched ground to illuminate the CEL. I mounted a little LED in the dash, provided it switched 12V power (from the stereo) to one pole, and ran a ground wire from the correct pin on the E36 harness to the other pole.

        I had to solder a wire to one of the three pins on the green connector on the back of the cluster and then ran that to the correct pin on the E36 harness.

        -Oil Level Sensor
        The oil level sensor has three wires: Static and dynamic levels and a ground. I grounded the brown wire to the E36 harness and ran two wires through the E36 harness, through the connector, to the correct E30 pins.

        I also have s52 headers if your interested in those as well. Good Luck!