Speed sensor PROBLEM

[Nonsense]

So I need to get smogged soon and a code is showing for a speed sensor (Code14).I replaced the speed sensor with another and its still showing a damn code.I reset the ECU like 10 times And still it pops up after 14-20 miles of driving.The Speedo works everything works like it should and the damn code still pops up.I need to get smogged this month so im feeling the pressure.Oh and its a 96 240sx obII any help on this would be amazing.