As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF IMBALANCE FUEL LIGHT ILLUMINATED, APPROX 1.1K LBS ON LEFT SIDE, RAN QRH, FAILED WITH FODO. LAND WITH 1.1K LESS ON LEFT SIDE. GROUNDED - YES. PER CONVERSATION WITH FLIGHT CREW CONDITION WAS TRIGGERED WITH USE OF APU ON GROUND FOR APPROX. 3HRS PRIOR TO DEPARTURE, IAW B737-900 AMM TASK 05-51-48-211-801 NO CONDITION OF INSPECTION REQUIRED WITHIN OPERATIONAL LIMITS. A/C OK FOR SVC.