If you defined custom coordinate system definitions in a previous release of AutoCAD Map 3D, those coordinate systems are automatically added to your custom definitions when you install AutoCAD Map 3D.
However, if you continue to use an older version of AutoCAD Map 3D to define custom coordinate systems, then you need to use the Coordinate System Update Utility (csupdate.exe) to add those custom definitions to the current AutoCAD Map 3D coordinate system files.
Warning: Do not copy the coordinate system files from previous releases of AutoCAD Map 3D directly into the current AutoCAD Map 3D coordinate system folder. Use this Coordinate System Update Utility to transfer your previous custom coordinate system definitions into the current AutoCAD Map 3D coordinate system files.
About Coordinate System Update