- Speed sensor failure: The speed sensor is responsible for providing the vehicle's computer with information about the vehicle's speed. If the speed sensor fails, the speedometer will not receive the necessary data and will stop working. Additionally, the transmission may shift hard or erratically because the computer will not have the correct information to determine when to shift gears.
- Transmission control module (TCM) failure: The TCM is responsible for controlling the transmission's shifting. If the TCM fails, the transmission can shift hard or not at all. Additionally, the speedometer may stop working because the TCM provides it with information about the vehicle's speed.
- Wiring problems: Wiring problems can also cause the speedometer to stop working and the transmission to shift hard. If the wiring between the speed sensor and the speedometer is damaged, the speedometer will not receive the necessary data and will stop working. Similarly, wiring problems between the TCM and the transmission can cause the transmission to shift hard.
- Faulty speedometer: It's also possible for the speedometer itself to be faulty. This could be due to a manufacturing defect or damage to the speedometer. If the speedometer is faulty, it may not receive the data from the speed sensor or it may not be able to display the information correctly.
To diagnose the exact cause of the problem, it is recommended to have the vehicle inspected by a qualified mechanic or automotive technician.
