Since 1996 all cars manufactured for the United States of America have been required to have an OBDII port. This stands for on-board diagnostics, and is used by drivers everywhere to have access to their vehicle’s computer system. Originally implemented to monitor and maintain EPA (Environmental Protection Agency) emission standards, OBDII ports are now used as an engine management system in every modern vehicle.

An engine management system such as OBDII technology can be divided into three main parts: inputs, processing unit, and outputs. Inputs are sensors on various parts of the engine that monitor a wide variety of conditions that affect its operation. You can see a common engine sensor pictured to the right. These sensors feed data to the processing unit, otherwise known as the vehicle's computer.

The main computer analyzes all of the inputs simultaneously so that it can operate the engine’s outputs: fuel injectors, ignition coils, and transmission shift solenoids. This allows for proper fuel ratio, ignition timing, and transmission operation as the car shifts through its gears. If the computer senses something wrong with the vehicle, malfunction indicator lamps (MILs) become visible on the dashboard.

MILs have been used for decades to notify drivers about the condition of their vehicle. These amber lights appear when a car’s computer has sensed a specific issue. Common MILs show low fluid levels, headlight status, and most importantly your check engine light, or “engine management system.”

If a solid check engine light appears on your dash, it does not necessarily mean you are in for a large expense. When the light comes on it simply means that sensors have picked up on a change in the emission control system, fuel mixture, engine performance, electrical circuit, or drive train. However, driving with a flashing check engine light indicates the user to stop driving immediately. A flashing check engine light means further driving could cause major systems to fail. When your check engine light appears on your vehicle’s dashboard, it is time to find the root of the problem using the OBDII port.

The OBDII port provides direct access to your vehicle’s computer. You will first need a code scanner, which can be purchased at a reasonable price from any auto parts store. Many auto stores even have a free code scanning service. The OBDII port is normally hidden from plain sight, and can be found underneath the steering wheel. Once the scanner is plugged in, turn your key to accessory mode, but do not start the engine. You will be able to pull “trouble codes” that the vehicle’s computer is receiving from its sensors. Note: it is recommended to turn off all electrical accessories during this time, as this could cause an inaccurate code pull.

Code scanners are valuable diagnostic tools, but they not direct interpretations of what is wrong with your vehicle. The codes simply show that there is an issue at a specific sensor somewhere on your engine. However, this does not mean that these codes are useless. As you can probably guess, car models of the same generation tend to have the same problems. Putting your codes into an internet search can help connect you with other’s who have had and solved the same issues that you are experiencing. Mechanics also have large documents that further explain the code for your specific vehicle. OBDII codes are invaluable to DIY and professional mechanic car repair, however the use of the OBDII port doesn’t stop at troubleshooting.