As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT FUEL TANK QTY INOP - BLANK DISPLAY. GROUNDED - YES. TROUBLESHOT TO BAD FQIS COMPUTER, REF B737-800 FIM 28-41 TASK 810. REPLACED FQIS COMPUTER IAW B737-800 AMM 28-41-81. OPS TEST GOOD. LH FUEL TANK QTY RETURNED TO NORMAL. ETOPS GROUND VERIFICATION SUCCESSFUL.