As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF FROM EWR, THE LANDING GEAR WOULD NOT RETRACT AND CREW RECEIVED AN LG AIR/GND FAIL MESSAGE ON EICAS. THE AIRCRAFT DIVERTED TO LGA AND LANDED WITHOUT INCIDENT. MAINTENANCE REPLACED THE LGEU DUE TO LGEU FAIL MESSAGE ON CMC. THE AIRCRAFT WAS THEN PLACED ON JACKS AND ALL SWITCHES AND HARNESSES WERE INSPECTED, WITH NO DEFECTS NOTED. GEAR SWINGS WERE PERFORMED WITH NO FURTHER DEFECTS NOTED.