As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON APPROACH WITH LT PACK OFF A STRONG ODOR OF BURNING EMANATED FROM THIS A/C SYSTEM. WHEN THE RT PACK WAS TURNED OFF AND LT PACK ON THE ODOR DIMINISHED. PERFORMED FIM TASK 49-11-00-815-926-002, CONFIGURATION 2 TO VERIFY POSSIBLE INSECT INGESTION. BLOCKAGE OF THE APU INLET PLENUM AND NOTHING FOUND. RAN APU AND CYCLED THE LT AND RT PACKS AND NO ODOR WAS SMELLED. OK TO CONTINUE.