As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKE OFF, OPERATOR REPORTED THE LEFT ENGINE DUCT OVERHEAT ANNUNCIATOR ILLUMINATED. THE OPERATOR REDUCED THE ENGINE POWER SETTINGS, LANDED BACK TO DEPARTURE. INVESTIGATION REVEALED THE LEFT ENGINE BLEED AIR PRE-COOLER HAD RUPTURED CAUSING THE DUCT OVERHEAT WARNING.