As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU START UNSUCESSFUL AT FL 400 AT -45 DEG C AFTER 3 ATTEMPTS AT ALTITUDE. UNSUCCESSFUL ON THE GROUND AS WELL.(<P>NOTED BY MX. REMOVED AND REPLACED DC FUEL PUMP CONTROL RELAY K191. NO HELP PER FIM 28-25 FT. 806. MDDR 147790 REMAIN OPEN. PERFORMED APU BITE PER AMM 49-61-05 NO FAULTS. PERFORMED OPS CHECK OF APU PER AMM 49-11-00. OPS CHECK GOOD.</P>)