As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON APPROACH TURNED ON WING ANTI-ICE AND GOT "MASTER CAUTION" WITH "L VALVE" AMBER LIGHT. GROUNDED - YES. T/S AND SUSPECT #1 ENG FAN AIR MODULATING VALVE. AS RECOMMENDED, REMOVED AND REPLACED #1 ENGINE FAMV IAW B737-9 AMM 36-12-03 VALVE. OPS CHKD GOOD. GROUND VERIFICATION TESTS ARE OK.