As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING AFTER START CHECKLIST, RECALL PRESSED, LEFT PACK LIGHT ILLUMINATED, PRESSING MASTER CAUTION AGAIN CANCELED PACK LIGHT. GROUNDED - YES. REMOVED AND REPLACED LEFT RAM AIR INLET ACTUATOR REF B737-800 AMM 21-51-21. MODULATION PANELS MOVED TO CLOSED POSITION SMOOTHLY WITHOUT BINDING. PERFORMED A BITE TEST ON THE LEFT PACK/ZONE TEMPERATURE CONTROLLERS REF AMM 21-61-00. NO DEFECTS NOTED AND OPS CHECK GOOD.