Wait a minute! How is it frequently getting to security lockout? Dead battery or bad key, don't know any other way. Both of those are fixed by just using the correct key with a good battery.
You can only have so many programmed keys, I don't recall the number.
You seem to have done a lot of stuff that you don't think is worth mentioning.

 

DONBREW. I have only done the relearn process once or twice after battery has been disconnected. Probably not necessary any more, Key works, starter spins, etc. But still no spark.

I unplugged and reconnected all the connectors to the fuse box in the passenger compartment. I only measure 0.1 volt at any of these fuses. Fuses look god and test fine for continuity. It seems that I should have 12 volts somewhere on that fuse panel.

 

Donbrew and others. After 5 months and 52 posts I am sure I have forgotten a step or two. In #48 don brew say that HHR PK3 is handled by the BCM. What does PK3 stand for? I saw on a wiring diagram that PK3 is in conjunction with an ignition lead of some kind.

Bcm is current not fastened to it's bracket. Since all those connection are plastic I felt that it should not need any further ground. The BCM does everything it is supposed to do except provide ignition

 

Passkey III anti-theft system.

And like I said, I installed a ECM that was programmed for my vehicle, I had to do the ECM/key relearn.

I did not have to do a crank relearn, but it was a new engine purchased from ZZP, then I purchased the ECM from ZZP, prior to starting the new engine.

But it sounds like a ECM/key relearn is not what you need.

 

I think there's some confusion about ECM's and BCM's.