I’m doing that and the starter solenoid clicks but it’s not turning the flywheel, however I can turn the crank by hand so the engine isn’t seized.
From the screen pic, I’m guessing that you removed the relay and you are jumping the connections to mimic the relay connecting. So it’s the starter solenoid clicking.
It seems to me that the starter isn’t trying to turn the flywheel. It’s like the starter gets power but doesn’t actually try to move.
Hard to explain, I have a video but no method to post.
My understanding is that the relay provides power to the starter solenoid, which drives the pinion gear forward to engage with the flywheel and at the same time closes a contact to provide power to the starter motor. With a weak battery, the solenoid doesn’t move far enough - just clicks and never closes the contact to the starter motor.
For sure, check the megafuse as suggested above, but with those BCM messages, seems like the most likely scenerio is a bad battery or bad ground - either starter motor ground or the main battery ground. Did you check the battery with a multimeter? I don’t think I’d trust that battery readout you got at the auto store/mechanic at this point. I’d check it with a multimeter to see what kind of voltage you have - if it’s low, see if it will retain a charge. Then move on to checking the grounds - not just looking at the contacts, but checking continuity/resistance.
If all that checks out, I suppose there could be a bad connection on the hot side of the starter motor (as opposed to the starter solenoid), or maybe something preventing the pinion from moving forward far enough to close the contact to the starter motor. But seems far less likely.
As others have mentioned, the brake switch, keyless vehicle module, and transmission control module all can prevent the ignition sequence, but I believe this is all upstream of the relay. My understanding is that the ECM checks the brake switch, KVM, and TCM for the proper signals, then allows the starter switch to send a signal to open the starter relay. If you are jumping past the relay, you should be removing all of this from the equation. But these are complicated cars, so I might be overlooking something here.