As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ATB- AIR TURN BACK DUE TO LEFT ENGINE VIBRATION SHOWING 10.0-12.0 COCKPIT UNITS. CORRECTIVE ACTION: INDICATION ERRATIC AND FAULTED FWD VIBE SENSOR. PLACED N1 VIBE INDICATION ON MEL 77-00-02C. LATER, REPLACED FORWARD VIBRATION SENSOR ON NBR 1 ENGINE. (LP 7376218)