What was found
(CAN) ON DEPARTURE YYZ, HAD A PRESSURE (PRESSURIZATION) BUMP, GAGES CHECKED NORMAL THROUGH 1000 FEET, HAD A CABIN ALT OF 1000 FT. DIFFERENTIAL, PRESSURE OF 2.0 PSI. QRH FOLLOWED AND LANDED BACK TO YYZ. A/C PRESSURIZED TO 8 PSI ON GROUND IN MANUAL MODE, NO FAULT FOUND. MEL RAISED AND CLEARED BY THE ACCOMPLISHMENT OF BITE TEST ON BOTH CABIN PRESSURE CONTROLLERS, NIL FAULT FOUND.