As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 3730 HAD TO ABORT TAKEOFF FROM BWI TO LGA DUE TO RECEIVING THE TAKEOFF WARNING HORN DURING TAKEOFF AT 20 KNOTS. THIS CONDITION WAS A REPEAT. ASSOCIATED POWER LEVER SWITCHES HAD ALREADY BEEN CLEANED AND CHECKED. MAINTENANCE REMOVED AND REPLACED THE FLAP GAUGE AND OPERATIONAL CHECKED THE SYSTEM. ALL CHECKS GOOD, AIRCRAFT RETURNED TO SERVICE.