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M20 start - no power to DME

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    M20 start - no power to DME

    Read no start guides and printed out etms for ground and power for dme pins and c101

    I have ‘88 e30 m20 late model w/ 1.3 motronic. No light for dme. Made sure the light wasn’t out by checking voltage at coil with ignition on. No voltage so definitely towards dme. To start off I don’t get power from the inline fuse so it’s bypassed with a wire from the big wire on the junction block back to the wire. Made sure there is power there too.

    Dme relay has battery voltage but not clicking when connected. Verified relay works by checking it with power probe.

    I forgot which pins on dme but there is one that is a hot wire constant voltage and it had battery voltage. Verified w/ power probe and circuit tester. The other two pins had no switched power with ign on.

    I’ve tried 2 separate dme’s & harness’.

    Always have noticed on c101 pin 7 does not have any voltage. I still have to check the obc relay & pin 27 dme which gets power from the obc relay but figured give it a shot here and put the flame suit on if I’m overlooking something.


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    #2
    I would try switching out the relay just to eliminate it (I know you tested it)- its a cheap part - I say this because you have "tried 2 separate dme's". and I have seen relays act real funny. This could cause a no start issue and issues in testing the DME

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      #3
      I have multiple that I’ve tried and received no results. Also bypassed the obc relay. No results.
      Noticed pin 7 has no voltage and is important for supplying power to the dme. Gonna start over fresh using via the no start page on e30 wiki


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        #4
        Presumably you have checked all the fuses?

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          #5
          Yeah of course


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            #6
            Ok - just to walk through this.

            Is your ignition on when performing the test? It doesn't specifically say this when testing main relay - but I am "guessing" it would be on.

            You are trying to figure out why no power to the DME - but you state on your first posting you have power? "hot wire constant voltage and it had battery voltage"

            So you tested the main relay by testing terminals 36 and ground (thats what I am seeing in the Bentley anyway - I believe it is the same pins as the 1.1) for Main Relay control and you ARE NOT getting a click when 36 is touched to ground? On any of the relays and no DMEs Nor with any different harnesses?


            Did you have continuity - of the new harness - when you plug the harness in?

            Im not sure of the difference but here is another reference on the 1.3 ECU.

            Where and how to access ECU: I have tried to illustrate where and how to access the ECU, it is in the glove box compartment. To access it open your glove box and undo the two screws holding the plastic cover that is at the "ceiling" of the glove box compartment, under there you will



            *If you have .bin files for chips or XDF files for these ECU's please email them to me at admin@rtsauto.com and I will upload them to this page as a resource for others.* Bosch Motronic 1.3, 1.1, 1.0, 1.7 are the primary ECU's that power all E30's. 1.3, 1.1, 1.0 for M20's (6 cylinders) and



            Other thoughts - Is this a no start? Is this why you are focused on the DME?

            I dont understand this statement
            "Made sure the light wasn’t out by checking voltage at coil with ignition on. No voltage so definitely towards dme"

            You mentioned no voltage to the coil - so you would have to check the wire between the coil and the ignition switch. When you turn the switch on there should be voltage to the coil. Its either a fault in the wire, the ignition switch itself or the wire to the ignition switch.

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              #7
              Just thinking more about this

              Pin 7 on C101 is switched power from the ignition switch.. in which you have no voltage.

              So - check the ignition switch. It would also explain why no voltage to Coil.

              Page 15-41 in Bentley.

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                #8
                Omg i cannot believe this, obc relay turned out to be the issue. I was going in circles. When I by passed I just stuck a wire & stuck back in for testing but the wire popped out while I was checking around. I feel so good that I actually checked everything pin by pin. Thanks everyone for helping me in the mean time.


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