As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AMBER TAI INDICATION LEFT ENGINE INTERMITTENTLY ON WITH ENGINE A/I SWITCH "OFF" POSITION AT CRUISE 380 FOR SEVERAL MINUTES AND AGAIN BELOW 7000 FEET ON DESCENT. NORMAL GREEN INDICATION OBSERVED WITH A/I SWITCH "ON". GROUNDED - YES. C/W WITH OPERATIONAL TEST OF #1 ENG COWL ANTI-ICING REF: B737-800 AMM TASK 30-21-00. NO DEFECTS NOTED, SYSTEM OPERATES NORMALLY.