As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DEN- TAXI FOR FLIGHT 4275, NR 2 ENGINE FAN VIBRATIONS. RETURNED TO THE GATE. MAINTENANCE INSPECTED THE BLADES AND PLACED THEM ON RSI FOR 10 HOURS. MAINTENANCE REPLACED THE FAN BLADES. OPERATIONAL CHECKS GOOD. AIRCRAFT RETURNED TO SERVICE.