On Board Diagnostics 2, often expressed as OBDII, relates to a regulation mandated by the US Environmental Protection Agency stating that the computer interface for all vehicles sold within the US must have a standard computerized diagnostic tool. As a result, the once overly-sophisticated plethora of diagnostic scanners used by mechanics has been reduced to a single, simple tool. This simplification has made diagnostic tools available to the consumer for a fraction of what it costs to have a professional scan your car. The OBDII sends a code to your diagnostic computerized scanner, which translates it into a mechanical, sensor or electrical issue with your car.
Plug the OBDII scanner into your car's diagnostic port, which is a D-style plug-in connector usually located somewhere beneath the steering wheel or in the fuse box underneath the driver's side dash board. Follow the directions on the scanner and turn your ignition to the On/Accessories position so that the scanner can read the code from your vehicle's computer. You will most likely need to wait a couple of minutes for the scanner to read the code or codes from your car's computer.
Write down the codes on a sheet of paper. Some code readers have a display that translates the code into a mechanical or electrical issue. However, many lower-end scanners will only give you the code. Numerous online Resources will give you a short explanation of what each code means for a variety of vehicles. There are also OBD II computer programs available to give you an explanation of the code through specialized software. (See Resources)
Fix the problem from your OBD II scanner. Sometimes the problem may be easily repaired, such as a faulty sensor. However, the OBD II scanner does not always convey whether the problem is specifically with the sensor or with some related component. As a result, there is still some guesswork and electrical testing that can be done with a multimeter in order to help further diagnose the problem.
Hook the scanner to the car again and clear the car's computer from the previous code.
Drive the vehicle for a couple of miles. In some cases, a code may reappear if the problem has not been fixed correctly. If you are trying to repair a vehicle and clear the codes in order to have it pass a state's inspection procedure, there is often a state-specific mileage that must be driven without any codes appearing before the vehicle can pass inspection.
