With the trouble some people are having with this, we did some testing.
Got an ECM and did nothing else but apply the EFILive VATS patch. Nothing else was touched. Not even the VATS parameters in the "System" section were touched. No power relays connected, no resistors connected to spoof the relay existence.
Install in car, starts right up and runs.
Some operating systems start first hit of the key. Some take two. This is consistent. The OS's that take two, wont start on the first cranking attempt. Key needs to be returned to the off position for 5 sec, then they start right up on the second attempt.
Another shop that we know has HPT. Tried same with HPT (after navigating how screwed up they get around VIN's and model years which is something that EFILive is free of)...., identical results.
Which OS are you using? We didnt go and test every GM OS there is, only a few.
If this is in a retrofit, are you trying to control any power relays (other than fuel) via the ECM?
Cheers.