Battery Light and turning off

Good morning everyone. I'm currently driving a stage 2+ Mk6 DSG. I currently have a stage 2 GIAC ECU tune on the car. This weekend my car started and then the RPMS would get lower and my car would shut off. Then the battery light came on. I tested it with a multimeter while I had the car running and was producing 14.0v and while it was off I had 12.4v. Could it be my alternator or a failing ECU? Any suggestions on what my next steps should be? Any suggestions would be valued greatly. Thanks for your time.

The battery light coming on is normal when the car shuts off. Check and see if you have any codes in the ECU and start from there.

Thank you.

Sent from my XT1650 using Tapatalk