What was found
AFTER STARTING BOTH ENGINES AND RUNNING AFTER START CHECKLIST, THE LEFT PACK LIGHT ILLUMINATED UPON SYSTEM RECALL, AND EXTINGUISHED UPON PRESSING MASTER CAUTION RESET. GROUNDED - YES. PERFORMED BITE OF #1 CONTROLLER, FAULTED TCV ON PREV FLT. VERIFY PASSSED AND RESET REF B737-900 FIM 21-62 TASK 801. REMOVED AND REPLACED LEFT PACK TEMP CONTROL VALVE. GROUND VERIFICATION CK AND LEAK CK GOOD REF B737-900 AMM 21-51-10-000-801 AND 21-51-10-400-801. ACCOMPLISHED LEFT PACK #1 CONTROLLER BITE PROCEDURE, TEST PASS NO FAULTS NOTED. REF FIM TASK 21-62 TASK 801.