As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAXI OUT, SMELLED A STRANGE OIL TYPE ODOR AND NOTICED THE APU HAD SHUTDOWN. STOPPED AND INSPECTED EXTERIOR AND FOUND NOTHING OUT OF THE ORDINARY. ACCOMPLISHED A SUCCESSFUL APU TEST THEN STARTED IT AGAIN. SUPPLY AIR WAS AT AMBIENT TEMP. SHUTDOWN THE APU. NO ODOR WAS NOTED WITH ENGINES RUNNING.