89 2500 crank no start.

[Jebadiah]

If the ECM is getting an RPM signal, I'm not so concerned about the pickup coil resistance. The pickup coil output is sufficient to trigger the ICM, which sends it's signal to the ECM--thus the RPM signal. And we know this is working because there is an RPM signal.

Still up for grabs, is that the ECM would process the signal, modifying the timing to adjust the spark advance, and then sending the signal back to the ICM that triggers the ignition coil.

Considering that you might have an ECM problem, or a failing wire harness, though. An intermittent wire connection between any of those parts could cause the no-spark, no-injection issue.

Seeing as the ecm out of my truck wasn't a fix, and there's that much wire harness to trace and check through, would it be feasible to swap the wiring harness? I have one here that was from a running truck. I think that's what the problem is. Even though the wiring passes a continuity test, that doesn't really mean anything I believe.