As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APPROACHING TOP OF CLIMB, CABIN TEMP BECAME DIFFICULT TO CONTROL (TOO HOT) RT PACK LIGHT ILLUMINATED. AFTER COMPLETING QRH PROCEDURE AND CONFIGURING FOR SINGLE PACK OPS, TEMPS RETURNED TO NORMAL. GROUNDED - YES. #2 PZTC FAULTED TCV. R AND R TCV AND CHECKED OK. IAW B737-800 AMM 21-51-10 PB 400.