As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
A/C WAS IN CRUISE AT 410 AND RECEIVED PRESSURIZATION EMERGENCY WARNING LIGHT, DESCENDED TO 330 AND WENT THROUGH EMERGENCY CHECK LIST. LEFT SIDE BLEED AIR WAS DEACTIVATED, SYSTEM RETURNED TO NORMAL. A/C LANDED SAFELY. REPAIRED AND RETURNED TO SERVICE. REPLACED LEFT MIXING VALVE CONTROL BOX P/N 5418553-18.