As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SEA - FLIGHT 2341 - AFTER TAKEOFF DURING GEAR RETRACTION, THE LEFT MAIN GEAR DOOR LIGHT REMAINED ON (AMBER). DID ALTERNATE GEAR EXTENSION AND RETURNED TO THE FIELD AND ACCOMPLISHED A UNEVENTFUL LANDING. MAINTENANCE REPLACED THE LEFT MAIN GEAR SEQUENCE VALVE. OPERATIONAL CHECKS GOOD. AIRCRAFT RETURNED TO SERVICE.