Have a 2015chevy silverado i swapped ecu and now trying to relearn the key with the steps to relearn but antitheft indocator doesnt come off even after 30 min waiting with key forward

If Your anti-theft indicator light is still on in a 2015 Chevy Silverado after waiting for 30 minutes with the key forward while trying to reprogRam it, You may have to try reprogRamming it again. Put the key in the ignition and turn it to the on position. The anti-theft light will come on and will remain on for about 10 minutes once it goes out, turn the ignition to the off position. Now again turn the key to on and wait for about another 10 minutes, until the light goes out. Finally, repeat this process one last time, You will be waiting for any change in the anti-theft light, it will either go out completely, flash once and under out or just flash. Once this change occurs, the re-learning process will be complete. Turn key back to the off position and remove the key for a few seconds and then try starting the vehicle.