I have the same problem on my 88 crx si. My speedo quit and my check engine light came on, my ecu says its the speed sensor. I also did the same and pulled the cable from the transmission and spun it with a drill and it worked, so I pulled out the speed sensor from the tranny and the little gear on the speed sensor had about 1/3 of the teeth broken, so I replaced the little gear but it still doesnt work. I've been driving like that for about 2 weeks and it sucks not knowing how fast your going. I guess its the gear in the transmission but dont you have to take apart the tranny to fix it.