As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FAULT LIGHT ILLUMINATED DURING APU START ATTEMPT AT FL380. SUCCESSFUL CSS ACCOMPLISHED AFTER FAULT LIGHT EXTINGUISHED AT FL320. GROUNDED - YES. REF B737-800 FIM 49-40 TASK 801, REPLACED APU AIR INLET TEMP SENSOR (AMM 49-61-31)) AND AIR INLET PRESSURE SENSOR (AMM 49-52-31) STARTED APU AND SHUTDOWN NORMALLY. APU BITE SHOWS NO CURRENT FAULTS.