As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UPON OPS PROCEDURE FOR MEL 21-21G, RIGHT PACK LIGHT ILLUMINATED. GROUNDED - YES. PERFORMED TROUBLESHOOTING PER B737-800 FIM TASK 21-62-00-810-831 FOUND RIGHT TEMP CONTROL VALVE BAD. REMOVED AND REPLACED RIGHT TEMP CONTROL VALVE IAW B737-800 21-51-10. PERFORMED OPS CHECK, OPS CHECK GOOD AT THIS TIME.