As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE CREW PASSING THROUGH FL019 NOTICED AN AMBER EICAS MESSAGE L BAS FAIL- LEFT BLEED AIR SYSTEM FAIL. I WORKED THE CHECKLIST WITH THE CREW AND ADVISED THEY NEED TO TURN BACK TO THEIR DEPARTURE DESTINATION. THE ACFT ARRIVED BACK TO PHKO WITH NO INCIDENT. I HAVE SECURED MAINTENANCE TO DO SOME TROUBLESHOOTING. I AM EXPECTING TO MOVE A CONTROLLER INTO THE LEFT BAC POSITION AND DEPART WITH NORMAL OPERATIONS.