How to Read Check Engine Codes

As of 1996, cars were outfitted with On Board Diagnostic (OBD) systems that enable vehicles to indicate to their drivers that something is wrong by triggering a check engine light on the gauge cluster. Although the convenience of communication between the vehicle and driver are met, sometimes it’s not clear as to why the check engine light is being triggered. Luckily, with an OBD code reader, drivers can receive a numeric code that refers to the issue your vehicle is sensing.

Refer to this guide to understand how to read the codes correlating to the check engine light your vehicle is triggering.

Types of Engine Codes

1. (P) Powertrain: engine, transmission, and emission system

2. (B) Body: lighting, climate control, airbags, etc.

3. (C) Chassis: steering, anti-lock braking system (ABS), and electronic suspension

4. (U) Network Communications: controller area network wiring and modules

  • General: these codes are universal to all vehicle makes and models, and required for basic emissions diagnosis. These codes consist of a “0” as the second digit in the code.
  • Manufacturer Specific: these codes consist of a “1” as the second digit in the code, and indicate they’re unique to a particular make and/or model of vehicle. They provide more elaborate diagnostic information that ranges beyond the general codes and basic emission diagnosis.

How to Read Your Vehicle’s Codes

Reading your vehicle’s check engine codes is as easy as plugging in a code reader to the OBD II diagnostic port, which is typically located on the driver’s side, under the steering wheel. Once the code reader is connected, it will display what code(s) are being triggered by the vehicle’s ECU. Typically, code readers will provide a short description of the issue along with the code.

Code readers can be purchased at any major automotive part store for a relatively low price, or you can go to many parts stores and request a scan, which is typically done free of charge. Most dealerships and repair shops will charge a diagnostic fee.

What to Do if You Have a Code

First and foremost, take note of the code for future reference. The code given by the code reader will tell you what component(s) are causing issues with your vehicle. If the code reader does not provide a short description of the issue, codes can easily be found online or in manuals specifically pertaining to your vehicle.

It is recommended not to clear the codes via the option on the code readers or by the old method, which is disconnecting the battery. Check engine lights will not disappear for good if the codes are cleared and the issue(s) are not addressed. Once the issues are diagnosed and addressed, the codes can be cleared from the ECU.

Now that you know how to read and diagnose the causes of the check engine light emitting on your gauge cluster, it’s time to fix the issue! Remember, clearing your vehicle’s codes will not allow you to pass emission testing as the code reader will set your vehicle’s OBD system monitors to zero, and your vehicle will not be allowed an emission inspection until the system is “ready,” meaning the OBD system monitors have run and completed without issues.