As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SHORTLY AFTER TAKEOFF AROUND 12,000 FEET, THE CREW RECEIVED A LEFT BLEED DUCT WARNING MESSAGE. RETURNED TO THE FIELD AND DID NOT DECLARE AN EMERGENCY. MAINTENANCE INSPECTED LOOPS MT141 AND MT142 AND NO DEFECTS WERE FOUND. PERFORMED TEST OF THE BLEED AIR LEAK DETECTION AND WARNING SYSTEM AND NO DEFECTS WERE FOUND. PROBLEM COULD NOT BE DUPLICATED.