As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHEN SWITCHING FROM ENG BLEED TO APU BLEED RAW GAS FUMES WAS NOTICED. INSPECTED APU AND ENG FOR FUEL LEAKS, NONE NOTED. HAD SAME CREW RUN BOTH ENG AND APU. PERFORMED SHUTDOWN IN SAME SEQUENCE. NO FUMES DETECTED. NO HISTORY OF FUMES. OK FOR SERVICE...