As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FAILED COLD SOAKED START AT FL 36000. EGT GOT TO 1050 AT WHICH TIME "FAULT" LIGHT ILLUMINATED AND IT TERMINATED THE START ATTEMPT. NOTE: APU START WAS NORMAL ON GROUND AT BOSTON. GROUNDED - YES. REMOVED AND REPLACED APU FUEL CONTROL UNIT REF B737-800 AMM 49-31-11. OPS CHECK, LEAK CHECK GOOD. REMOVED AND REPLACED APU LUBE MODULE REF AMM 49-91-11. OPS CHECK LEAK CHECK GOOD.