As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DIAGNOSTIC REPORTS NR 1 ENGINE CORE VIBRATION DATA INTERMITTENTLY REPORTS ZEROS FROM THE FRONT AND REAR SENSORS. ACFT GROUNDED. PERFORMED AAVM SYS BITE CHECK. BITE CHECK LOGGED N2 SENSOR LOSS OF SIGNAL FOR NR 1 ENG. REPLACED NR 1 ENG N2 SENSOR. OPS CK GOOD. REF AMM 77-11-02.