As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FAILED START AT 380, 380, 350. ALL START ATTEMPTS RESULTED IN A FAULT LIGHT. APU PEAKED AT EGT 1000 DEGREES C ON GAUGE. FAULT LIGHT EXTINGUISHED WITHIN 5 MINS. ON THE GROUND APU START WAS SUCCESSFUL. GROUNDED - YES. REMOVED APU FCU AND INSTALLED SERVICEABLE APU FCU REF B737-800 AMM 49-31-11.