As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FAULT LIGHT DURING 2 APU START ATTEMPTS ON THE GROUND AFTER LANDING. GROUNDED - YES. PERFORMED B737-9 IFIM 31-00-00-810-803 FOUND FAULT 49-41254 START CONVERTER UNIT FAULT. REF APU BITE REF B737-9 AMM 49-61-00-700-801 PERFORMED IFIM 49-40-00-810-818. PER FIM FAULT IS NOT ACTIVE AND WAS INTERMITTENT.