In 1996 the EPA (Environmental Protection Agency) mandated that the computer interface for all vehicles sold in the United States should meet a common standard. This means that consumers could go to an auto parts store and pick up an inexpensive scanner to pull the codes from the ECM themselves. This saved consumers hundreds of dollars because they didn't have to pay a car dealer to do it.
While this is good for an inexperienced mechanic, you still need to know how to properly use auto diagnostic tools. Scanners range from $20 units that do nothing more than read the code from the ECM, to very sophisticated units that require connection to a computer and software updates regularly. A sophisticated scanner will cost thousands of dollars and isn't practical for an inexperienced mechanic.
There are a few simple steps to using the obd2 code scanner. First, you need to locate the OBDII port on your vehicle. In almost ever car currently in production, the port is located under the dashboard near the drivers' door. Look for a white or yellow connector that looks like it belongs in your home pc.
Once you have located the OBDII port on the vehicle you can move to the next step. Making sure the car and the scan tool are powered off; plug the connector from the scan tool into the ODBII port on the vehicle. Once you have the scan tool connected to the vehicle, power on the scan tool.
On some tools you will need to follow on screen prompts but in most cases, this is the time to turn the ignition switch in the vehicle to the on position. Do not start the car yet. The tool will start to communicate with the ECM and read any trouble codes that exist in the memory. On lower priced scanners, you will only see the code number on the display. You will need to contact your local dealer or check the documentation that came with the scanner to determine the meaning of that code.
In some cases they can have multiple meanings so once you have the code, check all the possible causes thoroughly before you replace any parts.