Alternatively you can trigger a scan on a selected group in SEPM:
1. From the context menu, select 'Run Command on Group'.
2. From the context sub-menu, select 'Scan'.
3. In the Select Scan Type window, select 'Full Scan'.
How to launch a scan on all clients using the Symantec Endpoint Protection Manager 11.x.
http://www.symantec.com/docs/TECH97851