If you purchased a car after 1996, chances are it has an OBD-II (On-board diagnostics II) port. Every car or truck on the road manufactured after that point is mandated by United States Federal Law to have one installed. But what is it?

OBD-II is a sort of computer which monitors emissions, mileage, speed, and other useful data. OBD-II is connected to the Check Engine light, which illuminates when the system detects a problem.

Depending on the problem, the light either stays on, flashes, or goes away entirely. Mechanics can use scan tools to make sense of the diagnostic trouble codes, but with the right equipment and some technical know-how, you can too. You can even collect data on other aspects of your vehicle’s performance.

 

Onboard Diagnostics refers to any vehicle’s ability to register and report issues that may occur, or have occurred within the system. One of its strengths is it can detect problems long before the driver is able to notice any symptoms, such as low-performance, low-fuel economy, and heavy emissions, or before the Check Engine or Malfunction light comes on.

As you would expect, OBD-II is heavily used by professional mechanics, but there are consumer oriented products that can take advantage of its diagnostic abilities.