As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB, THE LEFT FUEL QUANTITY INDICATOR BLANKED. DURING CRUISE FLIGHT THE FUEL QUANTITY INDICATIONS BECAME NORMAL AGAIN. THE LEFT QUANTITY INDICATOR STARTING READING NORMALLY ABOUT 15 MINUTES INTO CRUISE FLIGHT. GROUNDED - YES. REPLACED FQPU IN REF TO B737-800 AMM 28-41-81.