Seeing your vehicle's check-engine light come on can throw a wrench in your travel plans. It can also feel a little scary: Does it mean your ride is headed for the scrapyard? Or is there a simple fix?

There it is. On your dashboard. Staring at you, mocking you, making you plot insurance fraud: your car’s check engine light. That little bugger has been on your dash for weeks now and you haven’t been ...