As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT 2789, LT AIR VALVE LIGHT ILLUMINATED IN ICING CONDITIONS. LT AIR VALVE LIGHT CAME ON AT 16,000 FT MSL FOLLOWED QRH AND RESET SWITCH. LIGHT STAYED ON OPERATED LEFT ENGINE BELOW 86 PERCENT NG UNTIL CLEAR OF ICING CONDITIONS AS PER QRH. AIR RETURN TO MSP. MAINTENANCE REPLACED THE LT AIR VALVE IAW GE MM 75-00-00. ALL CHECKS GOOD.