SQL2012 : Enabling Maintenance Plans
If you are intending to use maintenance plans, or other features requring the extended stored procedures in SQLServer 2012 you must first enable them. They are disabled as part of the concept of minimizing the exposed surface area of an instance.
sp_configure 'show advanced options', 1; GO RECONFIGURE; GO sp_configure 'Agent XPs', 1; GO RECONFIGURE GO
This is concurrent and does not require a recycle of the instance.