As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON APPROACH P91 TRIP, GEAR HANDLE SELECTED TO DOWN POSITION, ONLY THE NLG AND RMLG GREEN ANNUNCIATOR LIGHTS ILLUMINATED. LEFT MLG ANNUNCIATOR DID NOT ILLUMINATE. FOLLOWED CHECKLIST. EMERGENCY WAS DECLARED AND DIVERTED TO KGRR. MAINTENANCE REPLACED THE LEFT MLG DOWNLOCK SWITCH. GEAR SWINGS PERFORMED WITH NO DEFECTS NOTED. A SUCCESSFUL OPERATIONAL CHECK FLIGHT WAS PERFORMED. AIRCRAFT WAS RETURNED TO SERVICE.