As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON DESCENT ON RECALL LEFT PACK LIGHT ILLUMINATED. EXTINGUISHED ON MASTER CAUTION RESET. GROUNDED - YES. REF B737-800 FIM 21-53 TASK 807, LEFT PZTC BITE VERIFY TEST GOOD, PREV FLT HAS NO FAULTS. VERIFIED NO OBSTRUCTION IN LEFT RAM AIR DUCT. VERIFIED LEFT PACK OPS CHECKED NORMAL ON GND WITHOUT FAULTS.