As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFT SUPPLY DUCT AIR TEMP INDICATION FLUCTUATES BETWEEN 20-60 DEG C, WITHOUT MOVING AFT CAB TEMP SELECTOR. ACTUAL CABIN TEMPS SEEM NORMAL. ACFT GROUNDED. VERIFIED P5-17 CAB TEMP CONTROL MODULE CAUSING FLUCTUATION. R & R P5-17 CAB TEMP CONTROL MODULE REF MM 21-61-15. OPS CHECK NORMAL.