My situation was a bit different. My speedometer sensor was actually good, but wearing-out fast. Thus, a new sensor would have been needed anyway. But my P0720 code was actually caused by a low trans fluid/gear oil condition that was keeping the drive mechanism for the speedometer sensor from turning, which, in turn, caused a odometer reading error, which threw the code. In cool/cold weather, I had no problems with the speedometer, but not so in hot weather. Once temps got above about 75, the needle would swing wildly - I didn't know whether I was going 70 or 7, or 110 or 0. So, in short, check gear oil in manual trannies. My tranny is a G5M in a Fusion running the venerable 2.3L.