DTC B3031: Controller In Learn Mode: Description
WARNING: This page is about a different car, the 1999 GMC Sierra and 1999 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
This code sets when ignition is active and Passlock(tm) key code has not been learned by BCM. Vehicle will start and SECURITY indicator will be on.