Why Are Malfunction Indicators Called Idiot Lights?

Malfunction indicators are called idiot lights because they identify a vehicle's problem so clearly even unintelligent people are expected to understand them. These lights are displayed on a vehicle's dashboard when a system goes awry and may need professional attention. Many auto part retailers have diagnostic equipment available for public use so vehicle owners can determine whether the problem is fixable or requires professional attention.

The most common malfunction indicator is the check engine light, represented by an outline of an engine. Its presence can mean a number of issues that vary in severity. The check engine light may mean the gas cap is loose, or it may indicate a more serious issue, such as a catalytic converter malfunction.

The oil pressure light looks like an oil can. It is activated when the vehicle's oil pressure is low. Low oil pressure can result from a leak, an engine burning excessive amounts of oil, or a lack of sufficient oil in the tank.

Battery lights are shaped like a battery and indicate a problem with the electrical system. When displayed, the vehicle may not start. Battery malfunction indicators can mean loose terminals or a build-up of corrosion on the terminals. They can also mean the battery is dead or unable to maintain a charge.