The Drawing Checker examines all text and annotations in the P&ID against the current project properties to find discrepancies caused by recent changes made outside of the drawing. It identifies updates for the current drawing.
The Drawing Checker runs automatically when you open a drawing. If you don't want this default behavior, you can run the system variable PLANTDWGCHECKERAUTOCHECK to turn auto-checking off. You can click the Drawing Checker icon pm the ribbon to run it at any time.