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, NR 2 ENGINE HAS FAULT 75-20412. THE HPTACC POSITION SIGNALS DISAGREE, ECONOMIC FAULT. ACFT GROUNDED. REPLACED NR 2 ENGINE EEC REF AMM 73-21-60-400-801-F00. OPS TEST NORMAL. ETOPS PART AND GROUND VERIFICATION ACCOMPLISHED.