So Im working on a 98 expedition it's my mother in law's. It keeps throwing a speed sensor code. I've replaced the one that goes on the driver side of transmission and still no speedometer and when I get up to about 40mph it wants to shift hard to the next gear then keeping the throttle at same position it revs up high then goes back into gear almost like the transmission is slipping. But it's been replaced last year from my understanding. Is there anything I can do to test the sensors with a meter or something I can't keep spending money on sensors.

 

Quite often a speed sensor code is set due to a short or open in the wiring harness.