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position transmitter?

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  • position transmitter?

    Does anyone have the spec or know the tests to perform to varify the position transmitter( part # 12 52 1 287 784)?

  • #2

    it's described in row 15: It says 'signal of position reference sensor. Check using an oscillosope. Put the transmission in neutral and start the engine', the signal should look like the middle one. Connect pin 25 and 26 of the motronic to your oscilloscope or hook up the sensor directly to the oscilloscope.
    Resistance of the sensor should be 15 Ohms.

    here's the wiring diagram of the motronic (195PS)

    tell us how it went.
    Last edited by hardtailer; 01-29-2006, 09:27 AM.


    • #3
      This is how I came to post this thread...

      Thanks Hardtailer...

      Since acquiring my 88 E30M3 two years ago, it never ran right but it ran. Reading about other's experience with their M3 made me wonder if mine is the genuine article. I read through BMW and Porsche forums searching for resolution to similar drivability issue. When I first got the M3 I ohmed out and tested for voltage from the crank and reference sensor but overlooked the third similar connector. Two weeks ago I found some cracks on the insulation of one of the sensor. I thought maybe it would be a good time to change out these 19 year old sensors. As I was replacing them I noticed the third connector(position transmitter). What the??? I traced it down to another sensor secured on the bellhousing a few inches above the crank and ref sensor. I did searches on the forums but could not find anything on this so posted this thread.

      I cleaned up and reinstalled the position transmitter sensor and went for a drive. Now I know what these E30M3 are all about. The willingness to rev reminds me of honda vtec engines but w/ more oomph.

      A new position transmitter is on the way. Now it is time to look into suspension and brakes.

      And to think I was on the verge of getting rid of the M3 and opted to keep my 944 turbo. What a mistake that would of been not to mention getting my butt kicked by a car with a dirty sensor.

      Have you checked your crank angle, reference, position transmitter seonsor lately?



      • #4
        Nice one gents.

        Literature does not usually put much importance on this sensor.


        • #5
          I am wondering about this sensor. I have a s 14 swap going but don't have a hole to put this in.

          I have holes for the other 2 sensors.

          Where is it supposed to go in a real M3?



          • #6
            This sensor is not required for operating the car--it generates a signal that it sent to the diagnostic port only.

            The sensor reads the teeth on the front crank hub and mounts nearby in a small bracket.