There is indeed some processing inside the sensor. I found this interesting chart for a 98 ls1. An inside schematics of the sensors. I also measured the cam/crank inputs of the pcm. They are grounded, so you need to feed some voltage to the pcm to sense signal. There is also more processing in the pcm. The signal is filtered and converted to 0-5v by a special chip before it goes to the TPU. So the square shape might not be that important unless some thresholds are reached.
The crank sensor being some sort of magentic pickup will be really sensitive on magnetized engine parts and paints on the wheel.
I have been thinking about the dual pattern of the wheel. Could it be that the 2 wheels are some mirrored image 180* apart, making the the wheel to be installed backwards for reverse rotation engine.
Best way to test for valid crank signal is to bench wire the pcm and log rpms while rotating the wheel. For most of the pcms anything under 50rpm is hardly picked.
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