As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) FLT 581 CUN TO YYZ WAS ON CLIMB FROM CANCUN AIRPORT EN ROUTE TO YYZ WHEN AN ECAM MESSAGE ENG 1 REV PRESSURIZED APPEARED.THE FLIGHT CREW DECLARED AN EMERGENCY AND RETURNED TO CANCUN AIRPORT. THE CAPTAIN CONTACTED MAINTENANCE OPERATIONS CONTROL FOR ASSISTANCE. THE THRUST REVERSER WAS DEACTIVATED AS PER MEL 78-30-01. THE AIRCRAFT RETURNED TO YYZ. TROUBLE SHOOTING OF THE THRUST REVERSER IDENTIFIED THE T/ R HYDRAULIC CONTROL UNIT (HOU) AS DEFECTIVE. THE HCU WAS REPLACED 30 OCT 2000, AND TESTED SERVICEABLE. A TEARDOWN REPORT HAS BEEN REQUESTED FOR THE HCU.