What was found
EWR - FLT 605 - AFTER TAKEOFF, CLIMBING THROUGH 2000 FEET, THE AUTO FAIL LIGHT ILLUMINATED. CREW COULD NOT CONTROL CABIN PRESSURIZATION IN STANDBY OR MANUAL MODE. FLIGHT RETURNED TO FIELD TO EWR AND LANDED WITHOUT FURTHER INCIDENT. NO EMERGENCY WAS DECLARED. MAINTENANCE FOUND THE AFT SERVICE DOOR AJAR ON FORWARD SIDE OF DOOR. AFT SIDE OF DOOR WAS CLOSED WHICH CLOSED THE DOOR WARNING SWITCH. RECYCLED DOOR AND OPERATIONALLY CHECKED DOOR. DOOR OPS CHECKED GOOD. AIRCRAFT OK FOR SERVICE. (M)