ok it could be the Vehicle Speed Sensor, Speedometer, or the Wiring Harness
Customer Concern: Speedometer is inoperative. Vehicle Speed Sensor (VSS)
Tests/Procedures: 1. Verify battery voltage on the Black/Orange wire and ground on the Green/Blue wire at the VSS. 2. Scope the VSS signal Green/Red wire and look for a square wave signal.
SpeedometerVehicle Speed Sensor (VSS)Wiring HarnessTech Tips: The 3-wire vehicle speed sensor inputs a square wave signal into the speedometer. There is a reference voltage from the computer that the speedometer pulses to ground, creating the VSS signal for the computer. If there is no signal from the VSS, replace the VSS. If there is a good signal from the VSS and the signal is good at the speedometer too and the speedometer does not work, then replace the speedometer. The VSS is at the transfer case (4WD) or the transmission (2WD).