As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ENROUTE, CREW REPORTED THAT THE ACFT LOST PRESSURIZATION AT FL280. DECLARED AN EMERGENCY AND PERFORMED EMERGENCY DECENT PROCEDURE. LANDED AND TAXIED TO THE GATE WITHOUT INCIDENT. MX FOUND THE PRECOOLER HAD FAILED AND CHANGED THE PRECOOLER AND GASKETS IAW AMM. ACFT OPS CHECKED GOOD.