How to Check an Engine Code

by Jody L. Campbell

Prior to the second phase of on-board diagnostics (called OBD II) implemented in 1996, reading engine codes was difficult and often manufacturer-specific. To standardize the codes and equipment used to read them, OBD II universalized the location of the diagnostic link connector (DLC) and the plug-in connection of the DLC. All vehicles manufactured in 1996 and newer employ OBD II. Most all the codes are generic until they reach numbers over 1000. After 1000, many of the engine codes then become vehicle manufacturer specific.


Check the vehicle's owner manual to locate the DLC.


Plug the cord of the OBD II code reader into the DLC. If equipped with a power button, turn the code reader on. Most generate power from the vehicle's battery and do not require being turned on.


Use the scroll button(s) to choose the different options displayed on the onscreen menu of the code reader.


Choose the "read codes" or "read DTCs" (diagnostic trouble codes) option and then press the "enter" or "send" button. The engine code(s) will then be displayed on the onscreen menu.


Look the code up in the OBD II code look-up guide. Codes can also be found online. While some pocket scanners will give a brief description of the codes, less expensive models will only reveal the code number.


  • check Prior to OBD II, obtaining engine codes were more vehicle specific. While General Motors used two-digit blinking codes, other vehicles required scan tools with vehicle specific plug-in connections and software for the scan tool. Because of this, many people were referred to service centers at the manufacturers dealerships to determine the code. In addition, the codes on the older vehicles often required further diagnostics and were not as precise as the OBD II codes.

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About the Author

Jody L. Campbell spent over 15 years as both a manager and an under-car specialist in the automotive repair industry. Prior to that, he managed two different restaurants for over 15 years. Campbell began his professional writing career in 2004 with the publication of his first book.

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