What makes the speedometer and tachometer stop working?

There are 2 sensors on the engine that sent a signal to the computer and speedometer and tach. When one of these goes bad it can make the speedometer and tach go all over the place and also just stop working. This can also cause all types of engine running problems because the information being sent to the PCM will be incorrect all so. The units are easy to replace once you find them, it seems that they are located in different areas of the engine with each year the vehicle was put out. Your local dealer should be able to tell you the location of each sending unit. .

Answer

If your speedometer is not working, it is probably the speed (distance) sensor. There are tons of sensors. Follow the speedometer cable down to where it attaches to the sensor...Unplug speedo cable, pull elec plug, remove 10mm bolt, pull out, replace is opposite.

(This is not the same sensor as the input or output sensors)