As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WITH ENGINE ANTI-ICE ON L/H ENG ANTI-ICE COWL VALVE OPEN LIGHT REMAINS BRIGHT BLUE AND L/H TAI AMBER LIGHT ILLUMINATES. GROUNDED - YES. PERFORMED B737-900 FIM 30-21 TASK 804. LEFT ENGINE COWL LIGHTS EXTINGUISHED. PRESSURIZED PNEUMATIC SYSTEM USING APU BLEED AIR PER B737-900 AMM 36-00-000-860-803. NO DEFECTS NOTED.