While driving down the road my speedometer will jump to the speed i'm at, and back down to zero. Stay then jump. It keeps jumping back and forth. I have checked for grounded out wires and nothing I dont believe. I have also done the speedometer check with the guages and that was fine. I dont know if it is my speed sensor shorted out or tps sensor. Need help if anybody knows what to do or has had this happen to them. Any help would be appreciated.