Troubleshooting no-spark problem.
Probing the ignition coil harness for voltage when cranking.via this tutorial:
https://troubleshootmyvehicle.com/ch...gnition-coil-3
Says to probe the #2 green wire to check for power to the coil. Well, both of mine are black- so I used the inboard wire because that's where it's shown in the picture...

Probing that wire on the connector (and obviously grounding the black lead), I get 12v for a second or so when cranked, then drops to around 10v for a couple of more seconds- then nada after four or five seconds of cranking. Repeated this several times.

Is this normal? Shouldn't I be getting constant 12v to the coil when cranking?

I have checked the ASD relay, it is functional. Now trying to figure out if it's the coil itself- or move onto test #4 for the switching signal.

I'm still trying to reconcile four seemingly unrelated error codes for high voltage at sensors. Too much weird stuff going on, still thinking it might be the PCM.

 

If your battery is getting weak, voltage fall-off isn't really a surprise. Might try swapping the ASD relay, with another one, (horn?) and see if the behavior changes.

 

Unless some wiring has been replaced, the wires at the coil should be black/gray and dark green/orange. Could well be covered up with dirt and grime. Dark green/orange gets power from the ASD, the other one gets grounded by the PCM. 12V battery power for a short time sounds right, the PCM needs to look at crank and cam sensors to figure out which cylinders need ignition and which ones need fuel. Some voltage drop from firing the coil is also expected but it going to zero is not.
You can test the coil by itself: disconnect it, put power to the dark green/ orange terminal, use a wire on the other terminal and tap it to ground. Should produce a nice spark to ground at the distributor end of the coil wire.

 

You can check the resistance on both of the terminals also, If it's out of speck replace it. Should be about .95-1.20 ohms

 

^^^
Thanks guys, I'll check it.
I keep thinking it's the computer because of seemingly unrelated sensor error codes (4). I'll confirm coil is good, and if so I'll move on and test the crank sensor. If that's good as well, guess I'll bite the bullet and replace the computer.