So, as some of you may know, my long-suffering AE86 project is the recent recipient of an MS3Pro with the matching DIYautotune wiring harness. The Megasquirt replaced an outdated, unsupported FJO 341B that ran for all of about ten minutes before shorting out and dumping a couple thousand bucks down the drain. To cut a long story short, I foolishly attempted to re-use as many components (other than the ECU) as possible when updating to the Megasquirt. This plan might have worked well if FJO supplied any real info about their components, but instead they gave us really useful details like "Crank Angle Sensor. Three pins, power, ground, and crank angle." Full stop, no specifics. I monkeyed around with it, supplying different levels of power and attempting to read the output off the variable wire with a multimeter while waving it around in thin air or close to big chunks of steel. My conclusion was that it is a Hall Effect sensor needing 12V power, plus a pull-up resistor and I wired it as such when installing the harness. While going through the pre-first-startup test phase with the MS3, I failed to get a cranking signal. I ran a few basic diagnostic tests, and came up with no obvious red herring, so I figured that maybe I had either ruined the mystery FJO sensor with my battery of tests, or else I had jumped to the wrong conclusion and wired something incorrectly. As I sat there contemplating the next step, I determined that the DIYautotune crank angle sensor at $37.50 looked really attractive when stacked up against who knows how much more troubleshooting and guess work. The DIYautotuen sensor is Hall Effect, works with 5V-24V power, and offered a full spec sheet plus red-to-red, black-to-black, white-to-white wiring. Easy, simple, should be a no-brainer, right?
I ordered one, it came, and I wired it in. I tested it. No crank angle reading. Nothing. No sync, no reading while cranking, nothing on the tooth log. 
OK, so where do we go from here? I am hoping someone with some Megasquirt experience can offer a reality check on my plan of attack. I don't have an oscilliscope, but I do have a multimeter.
It might be back-to-basics, but it seems like the first step is to double-check continuity between the three wires at the sensor and the corresponding pins at the connector for the ECU. The next step is to plug in the harness, turn on the key, and test that the red wire at the sensor is getting switched 12V power, and that the black wire at the sensor provides 'sensor return' AKA grounded-through-the-ECU, and that the white wiring at the sensor is outputting very different readings when very close to steel vs. out in the open air. I assume that my current setup will pass all these tests, but you know what they say about about assumptions....
If the basic wiring connections and the function of the sensor test OK with the multimeter, what is the next step? The MS3 manual suggests: "Keep working on the crank/cam sensor inputs until you have stable rpm with no loss of sync." Which sounds great, but doesn't really include any details on what to do if you don't get any sensor input.
Oh, FWIW, the end of the sensor sits between 0.010"-0.020" from the tip of the teeth on the trigger wheel, so no, it isn't too far away. The signal wire is shielded for all but the last inch or so leading into the sensor, and the complete and total lack of a reading leads me to believe that noise is not the primary culprit.
Is there some setting in Tuner Studio that I could have configured incorrectly that would account for no crank angle reading at all with two different sensors?
What other avenues are left open to me besides jiggling the wires, sacrificing a small animal, or praying to different deity? Have I been sitting in the garage alone, staring at a non-running car for so long that I have overlooked something obvious?
Thanks in advance for the help! 
The moral of the story; always triple-check your grounds. Check your grounds, folks! 
