As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IAD FLT 6143 THE CREW REPORTED NR 1 LP VIBRATION ABNORMAL INDICATION AFTER TAKEOFF. THE AIRCRAFT RETURNED AND LANDED WITHOUT INCIDENT. MAINTENANCE INSPECTED AND REPLACED THE NR1 ENGINE FRONT FRAME VIBRATION SENSOR. OPERATIONAL CHECKS WERE GOOD.