As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER LANDING APU DIDN'T START, FAULT LIGHT ILLUMINATED FOR A FEW MINUTES. GROUNDED - YES. FOUND FAULT 49-41254 ACTIVE, PERFORMED B737-9 IFIM TASK 49-40-00-810-818. FOUND NO WIRING FAULTS. REPLACED START CONVERTER UNIT M1710 REF B737-9 AMM 49-41-61/401. ALL TESTS PASS FAULT IS NO LONGER ACTIVE. APU STARTS AND OPERATES NORMALLY.