How To Decode OBD Codes

As the owner of an older vehicle you might have thought to be proactive and buy yourself an OBD scanner, so you can diagnose any malfunctions on your own before they grow into a more serious problem. However, you might be surprised to find that although the scanner works, it only gives our error codes that might as well be gibberish to someone who doesn’t understand them. So how does one decode the results from an OBD1&2 scanner? Keep reading to find out. 

The Code

When you scan your vehicle with an OBD scanner, the result comes in the form of a five digit code which has a very specific meaning. Diagnosis is not possible unless and until that code is broken to give the reason result. The usual (manual) method of decoding the results from an OBD scanner requires extensive knowledge of the five-letter code that the scanner produces. Each letter has a different meaning:

  • The first letter denotes which system is producing an error. For example P for powertrain, C for Chassis, A for Airbags, etc.
  • The second number is used to identify whether the problem is specific to the manufacturer or it is generic. This is because there is a standardized list that was compiled for common problems that most cars have. Any errors that are not part of that list are added by manufacturers for the problems that occur in their models.
  • The third number helps you more specifically locate the area of the problem. For example, if you got P (for powertrain) in the first letter, the third portion of the code tells you whether the malfunction is in the ignition, the fuel injection or metering, air injection or metering and so on, and so forth. Of course, each malfunction demands a different level of urgency and requires a different method of repair. 
  • The last two are characters that give you the exact issue your vehicle has, so it is unique for every malfunction that you will encounter. 

As you can imagine, there are dozens of ways to combine the different parts of the code, and it is not practical for someone to memorize the entire list by heart. Nonetheless, knowing the first letter is usually enough information for most people to have some sense of direction as to their course of action. 

A Simpler Method To Decode OBD Scanner Results

If you find yourself overwhelmed by the sheer number of codes that you could encounter, don’t worry. There are a few websites that provide this service in exchange for a small fee. An even simpler method is to have an application that connects directly with your OBD scanner and decodes the error results for you instantaneously. Of course, everything comes with a price, and you can expect such a system to cost more than simply using an OBD scanner. Overall, decoding OBD scanner results may be straightforward, but it can be time consuming, so most people opt for an automated decoder online or an application.


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