As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED. AFTER TAKEOFF, EICAS MESSAGE LT PACK/BLEED LOSS WING LT. ACCOMPLISHED QRH AND MESSAGE REMAINED ILLUMINATED, FLIGHT RETURNED TO LAX. ACCOMPLISHED CHECK OF LT AND RT ENGINE AIR SUPPLY SYSTEMS, IAW AMM 36-10-00-700-801. OPERATIONS CHECK GOOD.