As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE PERFORMING T/C 78273000, FOUND FAULT 73-31371 FOR THE NR 1 ENGINE. ACFT GROUNDED. VERIFIED FAULT STILL ACTIVE, PERFORMED A T49.5 SYSTEM CHECK IAW AMM 77-21-200-801-F00. S1 AND S4 FOUND OUT OF LIMITS. REPLACED IAW AMM 77-21-01-400-801-F00. OPS NORMAL.