As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LAX - ON TAKEOFF HEADING ANNUCIATION ON FLIGHT MODE ANNUNCIATOR APPEARED, HEADINGS BEGAN TO DIVERGE. HEADING WOULD NOT RESET. AFTER 10 MIN ALL RETURNED TO NORMAL. EMERGENCY DECLARED FLIGHT RETURNED LAX LANDED WITHOUT INCIDENT. AIRCRAFT REMOVED FROM SERVICE. REPLACED BOTH HEADING GYROS. SYSTEM GROUND CHECK NORMAL OPERATION.