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 STAYED ILLIUMINATED AFTER TURNING WING ANTI - ICE ON. CYCLED SWITCH AND VALVE REMAINED CLOSED AFTER SECOND ATTEMPT. ADDED POWER AS WELL AND L VALVE LIGHT REMAINED ILLUMINATED WITH WING ANTI - ICE SWITCH ON. GROUNDED - YES. C/W WING TAI LEFT VALVE HEALTH CHECK, AFTER CYCLING L WING TAI VALVE 3 TIMES = NO FAULTS FOUND. WING TAI OPS CHECKS OK. REF B737-9 AMM 30-11-11-200-801.