What was found
IAH- FLIGHT 4172, AFTER TAKEOFF, LD/AIR GROUND FAIL MESSAGE AND THRUST REV DISAGREE MESSAGE APPEARED EICAS AND, REMAINED ON ENTIRE FLIGHT QRH'S COMPLETED. NO SPEED BRAKES INFLIGHT. NORMAL LANDING OCCURRED IN IAH. REMOVED AND REPLACED THE LANDING GEAR ELECTRONIC UNIT, PERFORMED A OPERATIONAL CHECK IAW EMB145 M/M 32-32-01. NO DEFECTS NOTED AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.