Often, the first indication of a problem with an automobile is a warning light appearing on the dashboard. These warning lights, such as the "Check Engine" light, are generated by the vehicle's electronic control module (ECM) in response to issues related to the vehicle's electronic systems, sensors or malfunctioning mechanical components. Each potential problem is linked to a unique code that the ECM stores. One of the easiest and most effective ways to diagnose car problems is to scan the ECM with an error code reader and then translate the codes to diagnose the problem.
Take the car to a location that offers free diagnostic testing using an error code reader. National parts store chains such as Auto Zone and Advance Auto Parts offer this type of free diagnostic services. Other stores may offer this service as well. Once you arrive, tell the technician that you want to scan your vehicle's ECM to find out what error codes your car is generating.
Hook the error code reader up to the ECM, which is located on the driver's side of the car underneath the dashboard. Press the scan button on the error code reader. In most cases, the store employee will perform the scan for you, as he already knows how to operate the machine. Make a list of the codes that appear on the screen of the error code reader.
Decode the codes generated by the error code reader. In most cases, the auto parts store will do this automatically and provide you with a free list of the codes and their corresponding meanings. You can also use the resources section of this article to look up the error codes yourself.
