I fixed a tractor using John Deere’s self-repair service. Farmers aren’t sold on it.

There is something wrong with the tractor. The water-in-fuel sensor, a small device embedded in the John Deere machine that monitors the integrity of its diesel engine, is disconnected. And I’ve got to fix it. I’m not a mechanic or a farmer. I’m poking at a laptop at John Deere’s corporate office in Santa Clara, California.