Yes you need the speed sensor,trail tough does it for about fifty bucks, It will stall when you come to a stop light with out it, all it is is a reed switch that goes next to a spining magnet on the inside of the speedo, they come stock in the side kicks and are easy to put in the samurai speedo the holes are allready there,just add one wire for the comp. and one ground wire, I left the red white and blue wire with the switch for the comp. codes to show.