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What is on-Board Diagnosis?

Sherry Holetzky
Sherry Holetzky

On-Board Diagnosis, also referred to as an on-board diagnostic system, is a required element in passenger vehicles and has been since model year 1996. While there are various purposes for on-board diagnosis or OBD, the mandated feature is a vehicle’s ability to self-diagnose emissions problems. The Environmental Protection Agency issues emissions standards that all vehicles must comply with and on-board diagnosis allows a vehicle to alert the owner if there is a problem that has the potential to violate these standards.

In vehicles with the on-board diagnosis feature, there is generally a light that goes on to warn the owner that the vehicle needs to be serviced. There is also a reporting capability, or a system for storing information that can be used by the person performing service to the vehicle to address the problem. In some cars, on-board diagnosis can do much more. It can warn of problems or potential problems with many of a car’s systems, including electronics or electrical systems, before an issue becomes serious.

On-board diagnostic codes are read using special tools.
On-board diagnostic codes are read using special tools.

Computers in cars have come a long way. They go beyond malfunction indicator lights, also sometimes called “dummy lights,” that indicate a problem without giving additional information. On-board diagnosis offers vehicle owners a much more accurate and efficient option for troubleshooting vehicle malfunctions. Instead of a simple warning light, which could lead to extensive testing or parts changing in order to eliminate the problem, vehicle owners can now narrow down the issue. This results in less shop time for cars and less expense for owners.

By providing precise data in real time, vehicle owners are less likely to suffer major repairs if they react quickly to on-board diagnosis warnings. Modern on-board diagnosis systems also include a wide-range of diagnostic trouble codes or DTCs. These codes will aid a mechanic or technician in determining not only the cause of the problem but also the proper action to take, removing a lot of the costly guesswork that vehicle owners frequently experienced in the past.

Consult your owner’s manual for more information on the on-board diagnosis system in your vehicle. It is also a good idea to ask about the diagnostic trouble codes when your vehicle is being serviced. Ask the mechanic to explain exactly what the problem is and what courses of action are available. Doing so may help you avoid unnecessary repairs and it can also help you better understand how to care for your vehicle.

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    • On-board diagnostic codes are read using special tools.
      By: Tyler Olson
      On-board diagnostic codes are read using special tools.