As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EWR---CO3873, CREW REPORTED, UPON GEAR RETRACTION LANDING GEAR AURAL WARNING SOUNDED. RECYCLED GEAR WARNING SOUNDED AGAIN. AIR RETURNED TO NEWARK. MAINTENANCE TROUBLESHOT AND REMOVED AND REPLACED AURAL WARNING UNIT IAW EMB145 MM 31-51-01. OPS CHECKED AND TEST FLOWN SATISFACTORY. AIRCRAFT RETURNED TO SERVICE.