I just went through the same thing-MAKE SURE YOU REPLACE THE WIRES GOING INTO THE SPEEDSENSOR FIRST!!! 99% of the time its those wires that get bad not the sensor itself!! If those wires are even a little freyed,you will get a fault code for the speed sensor.This is my 2nd taurus and all both the same problem and every single time it was the wires that plug into the sensor.And to one of the above comments,you paid $300 to replace the speed sensor?? the part only costs $40 or less anywhere you go and takes less than 10 min to install!!! | 
