As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT C-GTDX DEPARTING FROM YYZ ON APRIL 4TH 2008, AROUND 7000 FT AN EICAS MSG AUTO PRESSURIZATION SYS 1 AND 2, AIRCRAFT RETURNED BACK TO YYZ AND REQUESTED FIRE TRUCKS ON ARRIVAL DUE TO OVERWEIGHT LANDING. TROUBLESHOOTING CARRIED OUT, BOTH PRESSURIZATION CONTROL UNITS AND STBY ALTIMETER REPLACED AS PRECAUTIONARY MEASURE. FLIGHT TEST CARRIED OUT SUCCESSFULLY. INVESTIGATION IS ON GOING.