What Is OBD2?

OBD2, or On-Board Diagnostics II, is a standardized system used in virtually all vehicles manufactured after 1996 that monitors engine and emissions performance and stores diagnostic trouble codes when it detects an issue.

What You Need to Read OBD2 Codes

An OBD2 scanner, ranging from simple low-cost handheld devices to Bluetooth adapters that pair with smartphone apps, plugs into your vehicle’s OBD2 port, typically located under the dashboard near the steering column.

How to Read the Codes

Step 1: Locate the OBD2 Port

Find the OBD2 port, usually located beneath the steering wheel, and plug in your scanner with the ignition off.

Step 2: Turn the Ignition On

Turn your vehicle’s ignition to the “on” position without starting the engine, which powers the scanner and allows communication with the vehicle’s computer.

Step 3: Read the Stored Codes

Follow your scanner’s prompts to retrieve stored diagnostic trouble codes, which typically appear as a letter followed by four numbers, such as P0420.

Step 4: Look Up the Code

Search the specific code online or in your scanner’s reference guide to understand what system or component triggered the code.

Understanding Code Categories

Codes beginning with “P” relate to the powertrain, including the engine and transmission. Codes beginning with “B,” “C,” or “U” relate to body, chassis, and network communication systems respectively.

What to Do After Reading a Code

Once you know the code, you can research the likely cause and determine whether it’s something you can address yourself, such as a loose gas cap, or whether it requires professional diagnosis and repair.

Frequently Asked Questions

Do I need a special tool to read OBD2 codes?

Yes, you need an OBD2 scanner, which can range from a simple inexpensive handheld device to more advanced Bluetooth adapters that work with smartphone apps.

Can reading my own OBD2 codes save me money?

Yes, many auto parts stores also offer free code reading, and understanding the code yourself can help you avoid unnecessary diagnostic fees for simple issues.

Does clearing a code fix the underlying problem?

No, clearing a code only resets the warning light. If the underlying issue isn’t repaired, the code will likely return once the vehicle’s computer detects the problem again.