How to Read and Understand Obd Codes


The sudden illumination of the Check Engine Light on the dashboard of your vehicles, while you are driving, can be intimidating if you do not know how to read and interpret OBD codes. However, in reality, understanding the codes is not a daunting task.

The Check Engine Light can refer to a wide number of issues of your vehicles such as fault in the ignition, emission controls, transmission, fuel system. In order to know the exact detail of the problem, you need to be able to decipher OBD codes. You just need an OBD scanner, and a proper guide to provide you with some useful knowledge for interpreting the codes.

How to Read and Understand Obd Codes?

First, get an OBD scanner to start diagnosing the error in your vehicle. An OBD scanner can save the time and money that you would have spent on mechanic shops for inspection.

There are a lot of scanners in the market. Although the purpose of all of these scanners is to diagnose the fault in your vehicle, there are differences among these scanners. After analyzing these scanners, we can say that it is fixd worth buying. It works much better than any other scanner.

Step 1: Insert The OBD Trouble Code Scanner

Look for the OBD port for using the trouble code scanner. It is a 16 pin female connector that easily fits into the OBD scanner. The OBD port is also called a diagnostic link connector. For different vehicles, it is located in different places such as the center dashboard, below the driver’s side dashboard. Find the OBD port of your vehicle by checking your owner’s manual. After finding the OBD port, plug the scanner into it.

Step 2: Turn On The Ignition

Instead of starting the engine, switch the ignition of your vehicle on. After turning it on, the OBD scanner will receive power as a result of which it will start communicating with the onboard computer of your vehicle.

Check the cable connection between the OBD scanner and the OBD port if the scanner does not get power. If there is no problem with the connection and the scanner still does not get power, you should check whether the vehicle’s power outlet is transferring power. The OBD scanner will not work unless there is voltage coming through the power outlet.

Step 3: Enter The Vehicle Identification Number

You have to insert the Vehicle Identification Number, the model, and the type of engine in the OBD scanner. When you enter the details about your vehicle in the scanner, it can give you the exact information.

Step 4: Find OBD Codes In The Menu

In this step, navigate the codes on the scanner. In most cases, you will find two options- Active Codes and Pending Codes. Active Codes denote live codes or malfunctions. These malfunctions cause your Check Engine light on. Pending Codes refer to errors that are yet to cause the light of the Check Engine to trip. If the errors continue to happen, the codes will be shifted from Pending Code to Active Code and the light of Check Engine will turn on.

Step 5: Interpret The First Character Of The OBD Code

Now read the characters on the display and record them. Able to read the characters is not enough, you have to be able to decipher what those characters mean. The first character denotes the impacted part of your vehicle. You will see the first character among the following

  • P- it indicates a problem in the powertrain system such as engine,  transmission, emission, ignition, gearbox, fuel system.
  • B- it indicates a problem in the body system such as A/C, airbags, power seating, seat belts.
  • C- it indicates a problem in the chassis such as anti-lock brakes, axles, brake fluid.
  • U- it indicates a problem in the network such as wiring bus, UART.

Step 6: Interpret The Second Character

You will understand whether the error is a generic issue or it is because of the manufacturer by interpreting the second character. Generic codes represent normal problems that happen on most vehicles. Sometimes defects on the parts of the vehicles are not reflected by the Generic codes. For this reason, some manufacturers have included their own specific codes to represent the fault of the parts of their vehicles.

Now read the first two characters and interpret the meaning from the following list

  • P0 — Generic
  • P1 — Manufacturer-specific
  • P2 — Generic
  • P30 to P33 — Manufacturer-specific
  • 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

Step 7: Interpret The Third Character

The third character denotes the specific area which has impacted the vehicle.

  • 1- fault in the fuel or air metering systems such as mass airflow sensor.
  • 2- fault in the air metering injection or fuel systems such as an error in the fuel injector.
  • 3- fault in the ignition system such as engine misfire.
  • 4- fault in the emissions system such as catalytic converter.
  • 5- fault in the speed control and idle control systems.
  • 6- fault in the computer output circuit such as failure of the internal computer.
  • 7- fault in the transmission.
  • 8- fault in the transmission.
  • 9- fault in the transmission.

Step 8: Interpret The Final Characters

The final two characters refer to the exact fault. In order to find the exact details of the faults among thousands of errors, check online sources. You will find many websites and apps related to OBD code interpretation. Insert the whole code on a website or an app and it will inform you of the full details of the error and the way of fixing it.


Using OBD codes has made it easier to diagnose the problem of your vehicle. Sometimes, the codes are generated because of temporary issues such as poor connection, loose fuel cap, moisture on the sensor.

Understanding OBD codes can be complex as there are plenty of different codes. You can break these codes to understand easily. There are also various online sources that can help you to decipher the OBD code.