How to Understand Your Car’s Diagnostic Codes

How To Understand Your Car’s Diagnostic Codes

Avandacar – Having a car is not only a matter of owning it and driving it, but you also need to understand your car. This is quite important so you wouldn't get tricked by irresponsible mechanics who want to drain your wallet for problems that don't even exist, or when you want to sell your car. Either way, if you want to learn how to do it, this is .


When talking about diagnostic codes, you would hear the term OBD2 a lot. OBD2 stands for On-Board Diagnostic 2, which is the second generation of self-diagnostic equipment. This equipment is usually located under your dashboard, in areas 4 to 9, beneath the column of your steering wheel. To be able to read it, you need an that will tell you what you need to know about your car's condition.

After you bought your own OBD2 scanner, look for the port, and then plug it. The port would usually be located under the dashboard, but in some , it could be under the knee bolster panel or the center console. Once you are connected, the scanner will give you your .

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The code's first digit indicates what kind of problem you have, these are manufacturer-specific and generic codes. If your scanner shows you that the first digit is 1 or P, that means the problem is in the engine or powertrain.

Codes of Trouble

You need to be familiar with the basics first before you can fully understand your car's diagnostic codes. For example, EVAP codes are to diagnose your car's emission system, which will help the air pollution to a minimum. On the other hand, the transmission codes used to monitor your car's transmission will be triggered by problems such as computer output circuits or speed sensors.

Trouble codes will tell you various problems in your car, the could be permanent or temporary and could have different meanings. These trouble codes are assigned a number of each car, so you need to know the code of your car to be able to identify the correct problems.

The codes you get will consist of letters and numbers. The first two digits of the code are generic, and the last three digits would be manufacturer-specific. If you are not sure how to understand your car's diagnostic codes, you could search it online to make sure. Once you're sure, you can use a software called OBD Auto Doctor that will help you decipher over 18,000 trouble codes.

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The Codes’ Meaning

There are several codes you could see on the scanner. The categories of these codes are P for powertrain, C for body systems, and U for network and vehicle integration. Each code will indicate a different part of your car and if you're not sure, you should consult your online or manual source.

Generally, trouble codes have a digit and each of them means a specific issue. P0 or P1 are generic codes and if the second digit is other than 0, it could indicate the mass air flow sensor or the car's auxiliary emissions control. P0033 indicates problems in the powertrain, P0106 could indicate problems from warning light to even a complete engine failure.

The most common codes you can stumble upon are such as: P0300 for cylinder misfire, P0420 for catalyst system efficiency below threshold, P0171 for system too lean, sometimes because of a bad oxygen sensor, P0455 for leaking in evaporative emission control system, and C1210 for ABS pump motor overrun related to issues of anti-lock braking system. If it's visible like dent or scratch, you can google on how to repair small dents and scratches on your car.

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When to Seek Help from a Professional?

Yes, you can learn to read your car's diagnostic codes, but you are not a mechanic and if the problems are too severe, you need some professionals to fix your car. You need to seek help when the codes are just too complex. Multiple recurring codes need a thorough diagnosis to find out the exact problems.

OBD2 scanners are great tools but they couldn't always provide you with complete and detailed information. Some specific issues need to be diagnosed with more specialized diagnostic equipment that only car shops and dealers have.

If it is about your safety concerns such as steering or braking systems, you should let the professionals handle it. Warranty coverage is also important to consider. If your car is still under a warranty, you need to have the repairs done by an authorized service center because you can void your warranty if you do it yourself.

There you go, how to understand your car's diagnostic codes for you who want to understand your car better.

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Adrian Padeanu

Adrian Padeanu is a seasoned automotive expert and the driving force behind AvandaCar. With over a decade of hands-on experience, Adrian's insights into car culture and vehicle mechanics fuel the website's engine. His passion for innovation and performance shines through every article, steering readers to the heart of the auto world. He graduated from Economy and Business Administration with a Master's Degree in European Business Management.