As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: LEFT FUEL TANK INDICATOR PERIODICALLY SHOWS A QUANTITY VALUE IT FLAGS A FUEL IMBALANCE AND MULTIPLE MESSAGES IN THE FMS. GROUND TEST OF FQIS SYSTEM FAULTED WITH MSG # 28-41115 (ARINC OUTPUT BUS FAIL). ACCOMPLISHED TEST OF REFUEL QUANTITY INDICATORS, DEU SELF TEST AND FMC OPS TEST, PER FIM 28-41-00-810-810 WITH NO FAULTS. REPLACED FUEL QUANTITY PROCESSOR UNIT, PER AMM 28-41-81. GROUND TEST PASSED.