There is a brain in the TSM (turn signal module) under the seat behind the battery (on 2002FLHTC). This unit monitors current flow of the turn signals and will cause that flash pattern if it has detected trouble. I put a trailer light jack on mine and every time I unplug the trailer the turn signal start the quick flash. Here is where you can find directions to reset the Code Diagnostics: 2002 Harley-Davidson Electrical diagnostic Manaul, page 3-20.
This will fix the problem.
If you have trouble finding it e-mail me...I'll send you a copy. [email protected]