Do you have a monitoring "app" insert Kennith's ire here... to see if the speed is reported via the computer. If speed is correct on the app and not the speedo, the VSS is good but the speedo is bad or vice versa. I use Torque pro for things like this all the time. it will also tell you verbally if you wish that it has detected an error whether is throws a dash light or not. Some DTCs will and some will not.