1997 F-Body ECM

[spfautsch]

Does anyone know if the wheel is removed from the optical path... do you measure a 1 or a 0 on high and low resolution inputs???

I can tell you with certainty that when the optical beam is broken the optotransistor outputs are logic low and when not broken high. It's been a while but I vaguely recall testing with a LED logic probe to determine in which state they are actively conducting (if they were PNP or NPN type transistors). You may find something useful in my rantings from here. I'll see if I can find anything there or in my notes and report back.

Edit: To update - I don't think I tested the opti outputs for transistor type after all. But I can do that this evening with my test opti that's missing all the high voltage parts.

I find talking about degrees relating to Opti a bit confusing. Wheel has 360 slots...cam runs half speed... each slot is 2 degrees crank (yes??).

It's actually quite simple. The way I built the logic for the diy-ltcc stuff was to count every state change (edit for clarification: either a rising edge or falling edge) on the high res ring as 1 crankshaft degree. This gives you 720 pulses per camshaft revolution. The low res side sees a rising edge signal on each TDC. By counting the degrees while the low res is either high or low one can determine the engine's position within a maximum of 2 low res rising edge triggers (180 crankshaft degrees plus width of indexed low res slot - maximum 46 degrees).

[spfautsch]

Interesting.

The J520 pickup has two open collector outputs - n-channel so they source / conduct current when low.

But...

The low res pin (farthest from the ground pin) conducts when the beam is broken.

The high res pin (adjacent to low res pin) conducts when the beam is not broken. Since I'm 100% positive the ecu doesn't care about the "polarity" of the high-res signal it wouldn't matter. But you learn something new every day.

This means what I said in the previous post "with certainty" only applies to the low res signal. :-)