As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LT AIR VALVE ILLUMINATED ON WITH LEFT ENGINE ANTI-ICE ON IN CLIMB, CRUISE AND DESCENT. QRH COMPLETED. AIR TURNBACK TO DTW. REMOVED AND REPLACED LEFT ENGINE ANTI-ICE/START BLEED VALVE IAW GE CT7 MM CH 75-00-00. GROUND RAN A/C. ALL CHECKS GOOD. P/N ON/OFF 6068T56P01, S/N ON GRTB8816, S/N OFF GRTG1563.