This bulletin applies to 2012 GMC Sierra 4WD trucks. You may experience a vehicle that has a P0633 set in the ECM. Also, you will not be able to clear the DTC. Code P0633 will set as an indicator that the ECM is in learn mode and not as a fault indicator.
Any malfunction that causes a no-crank condition will prevent DTC P0633 from clearing. This DTC will clear upon a successful engine crank and start.
Prior to diagnosing P0633 or replacing the ECM, ensure that all power moding, VTD and engine cranking systems are operating properly.