Security system issues

When this happens, is the security light staying on? When you wait 12 minutes, do you leave the key off or on? Have you ever checked fuel pump pressure when this happens?

1-If Tech 2 scan tool is not being used, go to next step.

2-NOTE:While VCM is in Auto Learn Procedure, battery voltage must be maintained at all time. This procedure must be followed exactly or procedure will have to be repeated from beginning. Performing following procedures will set DTC P1630. Turn ignition off for 30 seconds, then turn ignition on. DTC P1630 should clear. If it does not, diagnose DTC P1630.

3-Turn ignition on, with engine off for 11 minutes. Turn ignition off for 30 seconds. Repeat turning on ignition for 11 minutes, and turning it off for 30 seconds 2 times. Turn ignition on, with engine off and wait 30 seconds. Attempt to start engine. If engine starts and operates normally, go to step 4). If engine does not start or operate normally, go to step 5)

4- Using scan tool, clear VCM DTCs. Turn ignition off for 30 seconds. Attempt to start engine. If engine starts and operates normally, system is okay. If engine does not start and run, go to next step.

5-Using scan tool, read DTCs. If DTC P1626 or P1630 is set, diagnose affected DTC(s). If DTC P1631 resets, return to step 2).

The key will need to be coded the dealer can do it for you if you give them the VIN when you buy the key from them. You can try resetting the system by following this guide.

https://www.2carpros.com/articles/how-to-reset-a-security-system

Please run down this guide and report back.

Scan the computer for a passlock code/s -start here and let me know if there's any present-

That sounds like the passlock theft system. That's an injector disable. Is the theft lite flashing, or anything? If the theft lite is flashing, wait till it stops flashing, then try to start.

I'm giving you the relearn procedure. It may or may not work. If it doesn't, that would mean it has a hard failure and will require using a Tech2 scan tool to diagnose it.

Disconnect the battery and hold the cables together for about 30 seconds then reconnect the cables before performing the procedure. Read it carefully if done incorrectly it won't work. If it helps let me know.
Turn ON the ignition, with the engine OFF.
Attempt to start the engine, then release the key to ON (vehicle will not start).
Observe the SECURITY telltale, after approximately 10 minutes the telltale will turn OFF.
Turn OFF the ignition, and wait 5 seconds.
Repeat steps 1 through 4 two more times for a total of 3 cycles/30 minutes (the vehicle is now ready to relearn the Passlockà † Sensor Data Code and/or passwords on the next ignition switch transition from OFF to CRANK).
Important
The vehicle learns the Passlockà † Sensor Data Code and/or password on the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.
Start the engine (the vehicle has now learned the Passlockà † Sensor Data Code and/or password).
With a scan tool, clear any DTCs if needed (history DTCs will self clear after 100 ignition cycles).

When it does not start, does the engine crank?

Welcome to 2CarPros.

The easiest and really only real solution would be to get new keys made by either an automotive locksmith or go to a dealer and give them your VIN along with proof of ownership and ID. They can then cut new keys using the code from GM. The locksmith option is probably cheaper and they will come to you.