It's likely the vehicle speed sensor on the tranny. go to autozone buy a new one. Shouldn't be to hard to install. (probably the same as a Ford Taurus?) Google or forums for proceedure.
Check the fuses
You have a faulty gearbox.
Is it a 12 valve engine or 24 valve? What do you mean by speedometer sensor? Do you mean Vehicle speed sensor? If so why do you want to change that?
A 1997 Mercury Sable came stock with size p205/65r15 tires. Taller or shorter tires will cause the speedometer to read incorrectly.
The speedometer is driven by the vehicle speed sensor. See "Related Questions" below for more about where to find it, and how to replace one.
Check VSS(vehicle speed sensor)on tranny,the most common problem of speedometer errs,providing your vehicle is equipped with a speedometer cable.Also,VSS,will cause erratic speedometer reads. - Big Daddy
The one on the tachometer that is surrounded by a gear is the check transaxle warning light
If your speedometer is cable driven and not electronic, it sounds like the cable needs to be lubricated. You remove the cable from the back of the speedometer and pull out the inner cable and slide it back in while lubericating it with some speedo grease.
According to page #104, fuse #24 covers the: Integrated control panel, speedometer, electronic automatic temperature control module.See "Related Questions" below for more
There is nothing alike between them because a sable is a type of antelope and a martin is a bird
Most likely a loose connection or bad sensor it is electronic
Common Sable has more white marks on its face, while Zambian is more black faced.