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 DISAGREEMENT LIGHT REMAINED ILLUMINATED WITH WING ANTI ICE SWITCH ON. LH WING REMAINED ICE COVERED UNTIL THAWED BY WARMER OUTSIDE AIR. GROUNDED - YES. THERE WAS MOISTURE ON INLET SENSE LINE. REMOVED AND REPLACED L/H WING ANTI ICE VALVE REF B737-9 AMM 30-11-11. VALVE OP AND LEAK CHECK GOOD.