As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 6193 - IAD-JFK - DURING CLIMB, MADE A UNSCHEDULED LANDING AT IAD DUE TO AIRCRAFT WILL NOT PRESSURIZE. AIRCRAFT RETURNED TO GATE WITH NO FURTHER PROBLEMS. MAINTENANCE INSPECTED AND REMOVED AND REPLACED LEFT ACM DUCT. OPS CHECK OK. AIRCRAFT WAS RELEASED AND RETURNED TO SERVICE. (M)