As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON RECALL AFTER ENGINE START CONTROL CABIN ZONE TEMP LIGHT ILLUMINATED. RESET WITH MASTER CAUTION RESET. GROUNDED - YES. BOTH PFTC'S GROUND TEST PASS, NO EXISTING FAULTS. FAULT HISTORY SHOWS INTERMITTENT FAULT 21-51117, 21-51123 "PFTC CTRL INOP" ON LEG 09. CABIN TEMP AND INDICATION GROUND VERIFICATION SUCCESSFUL B737-900 AMM 21-61-00-700-807-002.