Truck normally runs well but more and more I started to get a Service Engine light. Then, it started to randomly downshift at any speed over 40mPH - from OD to 4th, to 3rd as if I was encountering a hill. I did my research. Crank position sensor for the P0301 and the transmission speed sensor for P0720. HOWEVER. All I did was clean the connectors going to these sensors and the problem was fixed. I used Deoxit, and generic spray contact cleaner. It’s worth your time to just try cleaning your connectors before you order parts. In the end, I ended up separating and thoroughly cleaning every electrical connector under the hood and on the transmission. This took me less than 30 minutes.

 

Nicely done, the internet parrots would have had you (buying)changing unneeded parts immediately.
I imagine there have been more than a few repairs accomplished not by the new sensor installed, but by undoing the connection during the changeout.

 

Similar story: About a year ago the ABS started acting up with a motor circuit error (don't remember the exact code). Some contact cleaner in the connectors, exercised the ABS a few times on a dirt road and it's been happy ever since.