As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT VALVE CAUTION LIGHT STAYS ILLUMINATED WITH WING ANTI-ICE SWITCH ON. GROUNDED - YES. PERFORMED B737-9 FIM TASK 30-11-00-810-808 AND LEFT WING THERMAL ANTI ICE VALVE HEALTH CHECK PER B737-9 AMM 30-11-11-200-801. WATER WAS REMOVED FROM THERMAL ANTI ICE VALVE INLET TUBE. OPERATIONAL CYCLE OF WING THERMAL ANTI ICE VALVE COMPLETED IAW AMM 30-11-11-200-802 STEP H NO DEFECTS NOTED.