As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF WHEN GEAR UP WAS SELECTED, NLG AIR/GND FAIL CAUTION MESSAGE APPEARED ON EICAS. AFTER DISCUSSIONS WITH BOTH DISPATCH AND MAINTENANCE CONTROL DECISION MADE TO DIVERT. PRECAUTIONARY EMERGENCY DECLARED. FULL STOP LANDING MADE AND SYSTEMS ALL NORMAL. DECISION WAS MADE TO TAXI BACK TO THE GATE. REMOVED AND REPLACED DAMAGED PROXIMITY SENSOR IAW EMB 145 AMM 32-10-02-3. PERFORMED OPS CHECK OF AIR GROUND SYSTEM IAW J/C E 32-63-00-710-001. OPS CHECK GOOD.