As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LE SLAT ASSEMBLY EICAS MESSAGE. AN EMERGENCY WAS DECLARED AND THE FLIGHT RETURNED DEPARTURE WITHOUT FURTHER INCIDENT. THE AIRCRAFT WAS GROUNDED. ACCOMPLISHED FIM 27-81-00-815-809. FOUND SENSOR FAULT S302 INBD SLAT NR 10. REPLACED SENSOR IAW AMM 27-88-01. OPS CHECKED OK.