I am not able to tell my speed for my mileage because my instrument cluster is showing - - - - -
My car has an automatic transmission.
It sounds like your speed sensor on the back of the transmission has failed. I would certainly recommend having it professionally tested to verify this diagnosis but this is the most likely cause. If the gauge cluster is still displaying something just not a number, this is an indication that the sensor has failed rather than the cluster due to the fact that the cluster still lights up. If you are in need of a mechanic to complete this diagnosis for you, consider enlisting the help of a professional from YourMechanic.