Please help
Run my test for "Reference Pulses". It tells a lot about several things. If the fuel pump runs after cranking breifly, the ECM recognized reference pulses.
Another pretty simple check: Watch the tachometer while cranking. If it just sits on zero, there won't be spark. ICM or ECM. There could still be Reference Pulses, however.
I would wait for a Petris. There is no substitute, IMO.





If you turn the key, and the motor "goes around", that's spinning, or cranking, or turning over. All the same thing.
If you turn the key and it only goes "click", or if nothing at all happens, then it will NOT crank / spin / turn over.
Not trying to be picky, and we figured out what you meant, but this will save you (and us) confusion in the future.
If you turn the key, and the motor "goes around", that's spinning, or cranking, or turning over. All the same thing.
If you turn the key and it only goes "click", or if nothing at all happens, then it will NOT crank / spin / turn over.
Not trying to be picky, and we figured out what you meant, but this will save you (and us) confusion in the future.

Another thought:
You indicated that the SYS message was flashing when you brought the car home. This indicates there was at least one active Code in the CCM (Module 1.) I've seen correlation between "bad battery" and SYS message. You indicate you had "18 Volts" indicated. A bad battery can cause high charging current but the alternator should still regulate the voltage to the nominal 13.8-14.5-ish. But what if the regulator is also faulty and is allowing "18 volts"?
High system voltage can be detrimental to solid state electronics. Things like the Opti, ECM, and ICM.
When you go to start this car, if it starts, monitor the system voltage immediately! If you see indications over 14.5, or the voltage climbs and gets over 14.8, shut it off! Investigate that the alternator regulator is also faulty. Don't allow high system voltage to destroy new parts or take out something else.
If it was being prepped for sale, it wouldn't be surprising to hear that they cleaned the engine bay, and some water or cleaner got on the harness and killed the opti. Lots of people think covering the opti helps. It doesn't, the outside shell of the opti has a seal to prevent water getting in. The wiring harness is a direct pathway for water to get in.





I hope your problem is easily and inexpensively resolved.
Another thought:
You indicated that the SYS message was flashing when you brought the car home. This indicates there was at least one active Code in the CCM (Module 1.) I've seen correlation between "bad battery" and SYS message. You indicate you had "18 Volts" indicated. A bad battery can cause high charging current but the alternator should still regulate the voltage to the nominal 13.8-14.5-ish. But what if the regulator is also faulty and is allowing "18 volts"?
High system voltage can be detrimental to solid state electronics. Things like the Opti, ECM, and ICM.
When you go to start this car, if it starts, monitor the system voltage immediately! If you see indications over 14.5, or the voltage climbs and gets over 14.8, shut it off! Investigate that the alternator regulator is also faulty. Don't allow high system voltage to destroy new parts or take out something else.



