As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 3837 YOW-DTW DIVERTED TO YYZ HAD LOUD DOOR SQUEAL FOLLOWED BY LOSS OF PRESSURIZATION APPROX 45 MIN INTO THE FIGHT. EMERGENCY DESCENT TO 1000 FT. EMERGENCY DECLARED AND DIVERTED TO YYZ. A/C LANDED SAFELY IN YYZ. INSPECTED AND CLEANED DOOR SEAL AND DOOR SURROUND PER AMM 52-11-00. OPS CHECK GOOD PER AMM 52-11-00 AND 21-32-00, RETURNED TO SERVICE TO DTW. DOOR SEAL WAS LATER REPLACED IN DTW IAW AMM 52-11-10.