As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
COCKPIT ODOR: WHILE TAXIING FOR TAKEOFF, WE SUDDENLY GOT A STRONG HOT BURNING SMELL, IT HAD AN ELECTRICAL SMELL TO IT. CORRECTIVE ACTION: PERFORMED MULTIPLE ENGINE RUNS AND APU RUNS. PERFORMED TC-5XL-21-120902MR1 (ENVIRONMENTAL CONTROL SYSTEM BLEED AND TRIM AIR DUCT BURN PROCEDURE.) THERE WERE NO ODORS OR BURNING SMELLS NOTICED DURING ANY OF THE ENGINE RUNS OR APU RUNS.