As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 253, DECLARED EMERGENCY AND RETURNED TO DEPARTURE DUE TO FUEL IMBALANCE MESSAGE. LEFT WING ABOUT 900 LBS MORE THAN RIGHT, FOLLOWED QRH. TOTAL FUEL IN FMS WAS LARGER THAN FUEL ON EICAS. 2000 LBS DIFFERENCE. FOLLOWED QRH, FUEL WAS OBSERVED COMING OUT OF RIGHT WING. REMOVED & REPLACED RT VENT FLOAT VALVE IAW AMM 28-12-05-400-801A. OPS CHECKED GOOD IAW AMM 28-12-05-710-801A.