As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BEFORE FLIGHT, A PASSENGER NOTICED SMOKE COMING FROM THE FLIGHT DECK. THE CREW DEPLANED THE PAX. MX INSPECTED THE AC INCLUDING RUNNING THE ENGINES BUT COULD NOT DUPLICATE THE SMOKE. THE AC WAS RETURNED TO SERVICE. THE RT PACK OVERHEATED AND WAS FOLLOWED BY SMOKE IN THE CABIN. MX REPLACED THE RT PACK FLOW CONTROL VALVE. THE AC WAS RETURNED TO SERVICE WITH NO FURTHER DEFECTS. (K)