Catching errors when executing a sql server stored proc from a SQL transform

I'm executing a SQL server stored proc in a SQL transform.  The stored proc errors in SQL Server after processing some of the rows but the error is not detected in data services and processes normally.  How are stored proc errors detected?

Syntax of my SQL Transform  -  exec [dbo].[CD551_SelectGCV01000] '[$G_GetSqlServer_StartDt]', '[$G_GetSqlServer_EndDt]' ,[$G_RUN_OPTION];

Thanks