As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE CREW REPORTED THAT AFTER TAKEOFF A LANDING GEAR AIR/GROUND FAIL MESSAGE ILLUMINATED. THE AIRCRAFT RETURNED TO IAH AND LANDED WITHOUT INCIDENT WHERE MAINTENANCE REPLACED RELAYS K0325 AND K0023. OPERATIONAL CHECKS WERE PERFORMED AND THE AIRCRAFT RETURNED TO SERVICE.