What was found
FLT 2258 - FLIGHT ATTENDANT AND NON-REV PILOT REPORTED DETECTING A FAINT ODOR OF SMOKE IN THE REAR OF THE AIRCRAFT. FRONT FLT ATTENDANT AND COCKPIT CREW DETECTED NOTHING. LASTED FOR ABOUT 1 MINUTE. MAINTENANCE GROUND RAN AIRCRAFT FOR 30 MINUTES WHILE ALTERNATING THE PACKS AND TEMPERATURE SETTINGS. NO DEFECTS OR ODORS NOTED. OPERATIONAL TEST OF ECS CONTROL SYSTEM CHECKS GOOD. COULD NOT DUPLICATE. NO PARTS REPLACED. AIRCRAFT RETURNED TO SERVICE.