As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AS DESCENT WAS INITIATED AT FL 400 NR 1 ENG BLEED TRIPPED OFF WITH A CORRESPONDING DROP IN LEFT DUCT PRESSURE. QRH OPERATED AND BLEED TRIP LIGHT EXTINGUISHED NO ENG OR WING A/I OF FLIGHT MIG 2C 237137 INITIATED. WHILE PERFORMING FIM TASK 36 10 00 810 801 FOUND PRECOOLER CONTROL VALVE STUCK IN BETWEEN CLOSED OPEN. REMOVED AND REPLACED PRE COOLER CONTROL VALVE REF 36 12 02 OPS AND LEAK CHECK GOOD. SEAMC CONTACTED.