What was found
EWR---CO2320, CREW REPORTED, (AIR/GROUND SENSOR FAILED. LANDING GEAR WOULD NOT RETRACT.) RETURNED TO EWR, MAINTENANCE REMOVED AND REPLACED NOSE LANDING GEAR PROXIMITY SWITCH (WOW) IAW EMB145 MM NR 32-63-02. OPS. CHECKED AND GEAR SWING GOOD. IAW EMB145 MM NR 32-30-00. AIRCRAFT RETURNED TO SERVICE.