As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF FROM PDX, THE TAKEOFF WARNING HORN SOUNDED WHEN THE LANDING GEAR AND FLAPS WERE RETRACTED AND COULD NOT BE SILENCED. THE FLIGHT RETURNED TO PDX FOR AN UNEVENTFUL LANDING. MAINTENANCE INSPECTED THE AIRCRAFT WHICH REVEALED THE FLAP LIMIT SWITCH CONNECTOR CONTAMINATED. MAINTENANCE CLEANED THE CONNECTOR AND PERFORMED A SUCCESSFUL OPERATIONAL CHECK IN ACCORDANCE WITH THE MAINTENANCE MANUAL. THE AIRCRAFT WAS RETURNED TO SERVICE.