06 Dyna FXDCI, handlebar mounted speedo. Speedo stopped working. Purchased new speedo and attempted odo copy from ECM. It does not work. DLC and speedo harness are getting power, speedo still does not work. Fuel tank removed and checked wires visually, no obvious cuts or breaks.

SOURCE: p0500 code no odometer/speedodometer replaced vss

pull out the instrument cluster
.check the soldering on the plugs.they are known for problems.the computer will generate a code if no feedback from the cluster.
tie them down with ties so it does not happen again.
it is from all the vibration

SOURCE: p0500 speed sensor code, odo and speedo not working

If one speed sensor goes out, it will make your speedo stop working. I believe the sensors are about 200 a piece. You'll have to take it to the dealership to find out which one is malfunctioning as there are 5 of them total (I'm pretty sure). They only charged me 30 to put it in as it is really easy and that way it is warrantied by them.
One other problem I had was with the electric brake controller on my truck went haywire and when I disconnected it, my speedo came back to life.
Hope this helps!