As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: ON LIFTOFF MULTIPLE FLIGHT DECK WARNING AND CAUTION LIGHTS ILLUMINATED. LOST COMM 1, NAV 1, UNABLE TO EXTINGUISH ANY LIGHTS ILLUMINATED. DECESION MADE TO RETURN TO PHL, EMERGENCY DECLARED AND AIRCRAFT LANDED WITHOUT INCIDENT. MAINTENANCE FOUND ELEC CONNECTOR ON (P5-9) WINDOW/PITOT HEAT MODULE HALF COCKED. INSTALLED ELECTRICAL CONNECTOR (J1 P005-009) IAW AMM TASK 30-41-41-400-801.