I had never used a code scanner, though this is the way to troubleshoot a car or truck nowadays. No more seat-of-the-pants shade tree mechanic-ing with today's cars. I had knocked a hose loose when I changed the air filter on my 2003 Toyota Highlander, and the check engine light came on. I checked what I had done, and re-connected the hose, but the light stayed on. The last time this happened, the Toyota dealer charged $90 to shut the light off. For only two-thirds that price I got a tool that I can use again and again and shut the light off myself. Out of the box it took only two or three minutes to read the basic instructions, plug it in, read the codes in plain English, and hit the reset button. No more Check Engine light! Couldn't be simpler. Highly recommended!