What was found
AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED AND THE AIRCRAFT RETURNED TO ORD SHORTLY AFTER TAKEOFF BECAUSE OF A MAIN CABIN DOOR 1L PRESSURIZATION WARNING LIGHT. LIGHT CAME ON AS THE AIRCRAFT ACCELERATED AND EXTINGUISHED BELOW 180 KNOTS. THE AIRCRAFT LANDED SAFELY AT ORD AND TAXIED TO THE GATE UNDER ITS OWN POWER. MAINTENANCE REPLACED THE L1 DOOR WARNING LIGHT PANEL PER AMM 52-73-22 AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK WITH NO ISSUES NOTED.