What was found
CARGO DOOR WARNING LIGHT ILLUMINATED & SOUNDED UPON PASSING FL 280 FOR FL 290 IN CLIMB. CREW RAN ABNORMAL CHECKLIST, DECLARED AN EMER & RETURNED. WARNING LIGHT FOR DOOR WENT OUT WHEN CABIN PRESS WAS AT 1.6 PSI. WARNING LIGHT ORIGINALLY CAME ON AT 8.2 PSI. ACFT LANDED WITHOUT INCIDENT. INSTALLED A NEW FASTENER AT FWD LOWER CABLE PULLEY OF CARGO DOOR ROTATING LATCHES. RIGGED IAW CARGO DOOR MM 52-31-01. PERFORMED ADJUSTMENT TEST OF DOOR LATCHING & INDICATION & PRESSURIZED TO MAX PSI. TESTED GOOD IAW DOOR MM 52-31-01. AIRCRAFT RETURNED TO SERVICE.