Probably the latter.

Both the Feed wire, and the signal return wire, start/end at the PCM. The feed wire feeds other sensors as well.... so, it probably travels around the engine compartment four or five times.

Wiring diagrams would be REAL nice to have...... You are probably going to have to pull apart the harness to find the problem. Fortunately, you already know which wire is the problem.

 

I have a pdf of the Service Manual, but I'm pretty sure it's been more frustrating than useful. Definitely not a format I'm accustomed to, and I'd kill for a usable diagnostic tree. I have a paper one coming in soon that I can mark up with enough highlighter that maybe I can make it useful? But this is gonna be quite the project.

 

This may help .I'll try to get the full diagram but it's a start.
Is on 97-99 .

 

Oh, quick bonus question. I got a read of ~0.1V on the ground wire. I'm generally inclined to expect 0v on a ground wire - is this correlation? Causation? Normal?

 

Is that with the sensor unplugged??

That *might* be normal..... the sensor ground is shared with other sensors as well.

 

Yeah, all these measurements are at the vehicle side of the crank sensor connector, KOEO.

 

I was kicking this around with my partner, and realized something - since the voltage is pretty cleanly 5v at the connector, and we know the drop is most obvious at the PCM, what are the odds the short is at the connector? God knows when I opened the hood, it dumped snow straight onto it - it's in the perfect place to get soaked. Is there a good way to determine if the short is in the connector? Testing for continuity, maybe? And if so, can I buy that pigtail?

 

Ignition off, check resistance between the two wires. If it's shorted, unplug it from the PCM, and test again. If the short is AT the connector, you should be able to see it with a simple inspection.

 

I'd do a ohms test from the A4 at pcm to the # 2 ground or that black/ LTE bl [middle wire]ground at the harness
[see diagram].
An the same test with the other 2 wires to rule those connections out too.
An wiggle the wire a tad when connected on ohms test to see if theres a break in the wiring too.