As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WING ANTI ICE L VALVE COME ON WITH WING ANTI ICE ON. RESET AND IT WENT AWAY. TURNED WING ANTI ICE BACK ON AND L VALVE CAME BACK ONE. GROUNDED - YES. VERIFIED INTERMITTENT FAULT REF. B737-9 IFIM 30-11-00-810-808 ACCOMP. L/H WING THERMAL ANTI - ICE VALVE HEALTH CHECK, CHECK PASSES REF. B737-9 AMM 30-11-11-200-801 STEP H.