As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BOS - FL 816, CREW RECEIVED EICAS MESSAGE 'L HYD QTY', QUANTITY READ .45. FLIGHT RETURNED TO BOS AND LANDED WITH NO FURTHER INCIDENT. MAINTENANCE FOUND THE DIFFERENTIAL PRESSURE INDICATOR LEAKING AT THE PRESSURE MODULE AND REPLACED IT. (M)