These symbols, often called "idiot lights," are aimed at being easy to understand. But for many drivers, young and old alike, it's not that easy.

Mass air flow sensors fail most often in cars but a $20 air filter replacement every 12,000 miles prevents the $250-400 repair bills most drivers face.

Cars are very complicated things, built from thousands of parts ranging from nearly microscopic to crush-you-if-let-it big. With so many parts sourced from different suppliers, even the best car needs ...