OBD codes: what they are and how to read them

OBD codes: what they are and how to read them

Especially on modern cars it can happen that suddenly the engine light on the control comes onwhile driving. An unfortunate event if you are unable to read and understand i OBD codes. The latter, unlike what is believed, are not so illegible and it takes very little to understand the problem without having to lose too much money.

If the engine light comes on, there can be a variety of problems, ranging from ignition failure, emission control, fuel system and transmission. However, the details of the problem cannot be known until the OBD codes are cracked. To do it, just get an OBD Scanner and then read this article.

To read the OBD codes you need the appropriate scanner

Before doing anything, it is good to remember to always keep the OBD scanner in the car, a useful tool to save both time and money otherwise lost in mechanical workshops. On the market and on Amazon there are several, which differ in price and features but all are able to diagnose the fault.

To proceed to identify the problem, you need to search for the OBD port to use the scanner: it is a 16-pin female connector that fits the scanner, and which can be located under the dashboard on the driver’s side, or in the center of the dashboard. To do this first, grab the owner’s manual where the OBD port is always identified. Once located, connect it to the OBD scanner.

Turn on the ignition, but not the engine

After connecting the port to the scanner, proceed to turn on the vehicle ignition but do not start the engine. By doing so, the OBD scanner will receive power thanks to which it will communicate with the car’s on-board computer. If it does not receive power, check that the connection is effective; if the connection is right but the device is not receiving power, you need to check if the OBD socket is working.

On the OBD scanner it is necessary to enter the chassis number, the model and the type of engine, so that the device reports the right information. Then you have to move between the codes reported by the scanner, and usually there are two options given by active codes and pending codes. The former denote real-time codes or malfunctions, precisely those responsible for turning on the engine warning light. On the other hand, pending codes refer to errors that have yet to cause the warning light to come on, and if such errors still occur they will be moved to the Active Codes.

Interpret the code

After understanding the two types of code, you have to learn to read the first character of the OBD code, that is what indicates the interested part of the vehicle. Below, the characters that appear and what do they mean:

⋅ P – Problem in the propulsion system, which can be engine, transmission, emission, ignition, gearbox or power supply.
⋅ B – Indicates a problem in the body system such as airbags, power seats, seat belts.
⋅ C – Problem in the frame such as anti-lock brakes, axles, brake fluid.
⋅ U – Problem in the network such as bus wiring, or UART.

The second character, on the other hand, allows us to understand if it is a generic problem or due to a factory defect. Below are the first characters combined with the second according to the responsibility either the manufacturer’s or a natural defect:

⋅ P0 – Generic;
⋅ P1 – Manufacturer specific;
⋅ P2 – Generic;
⋅ From P30 to P33 – Manufacturer’s specification;
⋅ From P34 to P39 – Generic;
⋅ B0 – Generic;
⋅ B1 – Manufacturer specific;
⋅ B2 – Manufacturer specific;
⋅ B3 – Generic;
⋅ C0 – Generic;
⋅ C1 – Manufacturer specific;
⋅ C2 – Manufacturer specific;
⋅ C3 – Generic;
⋅ U0 – Generic;
⋅ U1 – Manufacturer specific;
⋅ U2 – Manufacturer specific;
⋅ U3 – Generic.

We must then understand what the third character means, always a number, specific to the area that affects the problem:

⋅ 1 – Failure in fuel or air metering systems;
⋅ 2 – Failure in metering air injection or fuel injector;
⋅ 3 – Failure in the ignition system (wrong ignition of the engine);
⋅ 4 – Failure in the emission system such as the catalytic converter;
⋅ 5 – Failure in the speed control and idle control systems;
⋅ 6 – Failure in the computer output circuit such as internal computer failure;
⋅ 7, 8, 9 – Transmission failure.

Finally, the last two characters refer to the exact fault: in this case the possibilities are many, and they vary from vehicle to vehicle. So if you can’t pinpoint the problem you can enter the entire code online to get the complete details of the error.


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