As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BOTH L&R WING ANTI-ICE AMBER LIGHT ILLUMINATE WHEN SWITCH IS PLACED ON. AMBER MASTER CAUTION LIGHT ILLUMINATES. ALL AMBER LIGHTS EXTINGUISH WHEN WING ANTI-ICE SWITCH TURNED OFF. GROUNDED - YES. OPS CHECKED WING THERMAL ANTI ICE VALVE PER B737-9 AMM 30-11-11 ALL SYSTEMS OPERATE NORMALLY. RAN #1  ENGINE AT IDLE, OPERATED WING ANTI ICE AND COWL ANTI ICE TOGETHER AND SEPARATELY, NO DEFECTS NOTED.