The car ran fine and showed no prior signs of problems. Then the day after a very windy rain storm the car would crank but not start. All interior lights/electrics work.

No spark, then wiggled/tapped the coil packs a bit and kept cranking - engine started and was running %100 fine, then died suddenly after 10 seconds.

Fuses were ok. I tried another ICM and coils, wiggled wires and checked(visually) the ICM plug and then tried to start it again but wont start.

It must have been fluke that tapping the coils/wires made it start, wouldn't the car at least run poorly or show signs of performance loss rather than a sudden loss of ignition?

It also may have been fluke that this just happened after very windy rain, but I think this likely related. After reading around it seems the problem could likely be the crank position sensor or corroded wiring under the fuse box - especially on my car with major rust around there which would allow wind + rain to get in.

I have some ideas to look at but would appreciate any help. Actually I really need help with how to use a digital multimeter to perform some of the tests. I've never used it before and wanted to try to test the coil pack like in this troubleshooting guide
https://www.gmforum.com/trouble-shooting-test-procedures-141/testing-coils-spark-plug-wires-278818/

not sure if this thing is supposed to have batteries in it or not... I see coilpack being tested outside of the car.

Ok found out that I DO need batteries in the multimeter. I'll be testing some of the things in the troubleshooting section. Battery in car is dead so I'll check what I can for now.

Most things that can be tested are in the testing area. I don't see a bad coil killing your car. You have 3 of them, and one going bad wont kill the engine. You said you replaced the ICM, so that shouldn't be the problem. The crank sensor is one of the first places I would look. It'* not a sensor that is easy to test with a DVOM, so I never made a write up on it. Do you have a SES light on the dash?

Thanks for your help,

I do have a SES light. I think its been on for a while, maybe intermittently, with no noticeable problem. All interior lights/dash come on, and when cranking the alternator gauge was moving.

I tested the coils according to the guide and readings were 5.5, one was 5.8 on the posts, and then 1.2 across on the primaries. Just want to make sure these are ok? Is there a way to test the ICM?

If I were to test the things on this list https://www.gmforum.com/showthread.php?t=29698 would having a drained battery effect the results? I see in the guide that I can test the crank position sensor by probing what I think is the ICM or the harness, while cranking?

The only way the coil is going to give no spark is if there'* a open, and you don't have that. I never made a test for the crank sensor because it'* not easy to do with a DVOM. But you should still see a signal change if you test the sensor signal wire.

The link you posted didn't work, you may have missed part of the link.