Honda: 00 civic speed sensor, Honda, Civic

Question
i have a 2000 civic si and the check engine light came on due to a speed sensor malfunction.. i replaced it with a gsr sensor but it was used and im not sure if its good or not? my speedometer and odometer still arent working. the old one would kick in after awhile but it would jump around a little bit.. do i need to reset the ecu or should i buy a brand new sensor? any help at all would be extremely appreciated  thanks

Answer
If you still have a check engine light code stored, clear it by removing the underhood 7.5amp Back-Up fuse for 20 seconds. If the code returns, you got a bad used part. Be sure to inspect the 3 pin connector very closely for any damage or corrosion. If you do not have a check engine light on after all of this and the speedometer is inop, check for voltage at the speedometer head (gauge). It should be an orange or orange/white wire at the gauge cluster. That wire will have fluctuating voltage as the wheels turn. You'll need to raise the car off of the ground and spin one wheel by hand as you monitor that wire with a DVOM (digital volt ohm meter). If the voltage fluctuates, you have a bad speedometer. They are a rather common failure on many 1992-2000 Civics and 1994-1997 Accords.