AutoData? catalog says I do have cam pos sensor data (at least in motronic), should be able to measure ~0.5V, few ms (it should be a few degrees instead, right ?) spikes with every second crank rotation. I couldn't verify that without a scope or notebook soundcard (yet).

I've checked resistance but it's like a wire, I couldn't see any more than some 0.1ohms, which is well in the error range of my digit multimeter.

Please make a few more measurements with different cam phase. A typical HALL sensor (unipolar, 5..15mT, digital output with internally applied hysteresis of 2..4 mT ) would short output to GND when B>Bthreshold and open collector otherwise. At least when powered with (usually 5V, rarely higher) supply.

Note ! This 'so called' CAM reference sensor is inductive coupled to cylinder 6 ignition wire (from distributor) ie. signal gets generated when cylinder 6 spark is fired.

It is very likely that they used this pickup to provide input signal to an off-the-shelf (RPM gauge) tachometer. The same way we use a few turns of wire around a coil HV wire to get signal for OnlineCourse/AlienIgnitionLogging

This is interesting question - since in schematic (E30 -89, with M20B25 engine) it seems that tachometer is wired directly from Motronic ecu (engine speed output from Motronic ECU connector pin 6, black wire to instrument cluster pin 7).

This could be used as a cam position sensor if the distributor is maintained (but than cam position is not interesting at all). In case

I guessed it's a cam pos signal because VR signal already exists (to drive RPM gauge?). Wiring is quite stock form (has a plug in a socket to 2 plugs and wire goes to the original harness). I've seen such a sensor on other similar BMWs also.

Nevertheless, I may or may not use this signal, we'll see. Motronic uses bank injection (2 banks for 6 cyls), so cam signal is not needed for that. Even if the 6 injectors are fired individually, cam signal is not needed (unless timed sequential injection is applied and tuned to squeeze the last bit of economy and emissions).

Original (Motronic) injection setup is batch firing (in two batches of three injectors simultaneosly).


(The ring on ignition wire near to distributor)

The connection to harness: