As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CONTROL CABIN AMBER ZONE TEMP LIGHT ILLUMINATES ON MASTER CAUTION RECALL. LIGHT RESETS ON MASTER CAUTION RESET. GROUNDED - YES. RAN BITE TEST B737-900 AMM 21-61-00-700-806-002 FOUND FAULT TRIM AIR VALVE FLIGHT DECK. PERFORMED PACK/ZONE TEMP CONTROL BITE CK REF AMM 21-61-00-700-806-002, NO FAULTS NOTED. REMOVED AND INSTALLED A NEW CONTROL CABIN TRIM AIR MODULATING VALVE REF AMM 21-61-21 PB 401 AS A PRECAUTION. RESET BOTH CONTROLLERS AND PERFORMED BITE CK, NO FAULTS NOTED.