As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING DESCENT WE TURNED ON THE ENGINE ANTI ICE FOR BOTH ENGINES. ONCE CLEAR OF ICING CONDITIONS AT 1200 FEET AGL, WE TURNED OFF BOTH ENGINE ANTI-ICE. THE #1 ENGINE COWL VALVE OPEN LIGHT REMAINED ILLUMINATED BRIGHT BLUE. WE CYCLED THE SWITCH AT DIFFERENT POWER SETTINGS AND INDICATION DID NOT CHANGE. GROUNDED - YES. REMOVED & REPLACED #1 ENG COWL TAI VALVE REF B737-800 AMM 30-21-11-400-801. OPS CHECK GOOD. COWL VALVE OPEN LIGHT EXTINGUISHED.