As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT PUSHBACK AND CLEARED TO START THE START SEQUENCE WAS INITIATED, THE APU SHUTDOWN ON IT'S OWN WITH A FAULT LIGHT QRH 7.2 WAS RAN. APU PUT OUT A LARGE AMOUNT OF SMOKE. RAMP CREW ADVISED A LARGE AMOUNT OF SMOKE WAS COMING OUT OF THE APU COMPARTMENT. GROUNDED - YES. REF B737-800 FIM 49-20 TASK 801. FOUND APU TURBINE SEIZED. REMOVED AND REPLACED APU REF B737-800 AMM 49-11-00, OPS CHECK GOOD.