Mercury

I do not see a cable so i asume that i should be looking for the vss (vehicle speed sensor). where is it? my electrical schematic shows the pcm with a pair of wires pk/o and gy/b going to nowhere for the vss. there is no locator for the vss in my haynes manual.

On a 1999 grand marquis, the vehicle speed information is relayed via the vss mounted on the tailshaft housing of the transmission. if it is equipped with the 2.73 rear axle ratio, there will be greenish blue coloured 17 tooth attached to the sensor when you pull it out. if it is equipped with the 3.27 axle ratio, it will be 21 teeth, and purple. if you determine the vss is operating, i would check the instrument cluster control head for input, and if good, you need a new speedometer. hope this helps.