How to Use an OBD2 Scanner (Step-by-Step for Beginners)

Step 1: Find the OBD2 Port

The OBD2 port is usually located under the dashboard on the driver's side. It is a small trapezoid-shaped connector.

• Most cars built after 1996 have an OBD2 port
• It is typically near the steering wheel
• You usually don't need tools to access it

Tip: If you can't find the port, check under the dash or near the center console.

Step 2: Plug the Scanner Into the Port

Once you find the port, plug the scanner into it. The scanner will usually power on automatically.

Depending on the scanner type, you may either:

• Use the scanner screen directly (wired scanner)
• Connect it to a phone app (Bluetooth scanner)

Not sure which type is easier? Read our guide: Bluetooth vs Wired OBD2 Scanners .

Step 3: Turn the Ignition On

Turn the car key to the "ON" position without starting the engine (or press the start button without pressing the brake).

This powers the car's computer so the scanner can communicate with it.

Step 4: Read the Trouble Codes

Use the scanner menu or phone app to select Read Codes or Diagnostics.

The scanner will show codes such as:

• P0300 – Random or multiple cylinder misfire
• P0420 – Catalyst efficiency problem
• P0171 – System too lean
• P0456 – Small EVAP system leak detected

These codes tell you which system triggered the check engine light.

Not sure what your code means? Browse common OBD2 trouble codes for beginners and find a simple explanation of what your car is trying to tell you.

Step 5: Understand What the Code Means

The code itself is only the starting point. You need to understand what it actually means before fixing anything.

For example, a code might point to:

• a faulty sensor
• a loose gas cap
• an ignition issue
• an emissions system problem

If your check engine light is currently on, read this guide first: What Does the Check Engine Light Mean?

Step 6: Decide What to Do Next

After reading the code, you can decide the next step:

• Research the code
• Fix a simple issue (like a loose gas cap)
• Visit a mechanic if needed

Sometimes the issue is minor, but sometimes it requires professional repair.

If you're wondering whether it's safe to drive, see this guide: Can I drive with the check engine light on?

Common Beginner Mistakes

Clearing the code immediately

Clearing codes without understanding them can hide useful diagnostic information. Write the code down first.

Ignoring a blinking check engine light

A blinking light usually indicates a misfire that could damage the catalytic converter.

Buying a very cheap scanner

Ultra-cheap scanners often have connection problems or poor code explanations.

👉 See our recommended OBD2 scanners for beginners if you want a simple and reliable tool.

Frequently Asked Questions

Do you need to start the engine when using an OBD2 scanner?

No. In most cases you only need to turn the ignition to the ON position. This powers the vehicle's computer so the scanner can communicate with it.

Can an OBD2 scanner turn off the check engine light?

Yes. Most scanners allow you to clear diagnostic trouble codes, which turns off the check engine light. However, the light may return if the underlying problem is not fixed.

Is it safe to drive after reading an OBD2 code?

It depends on the code. Minor issues may allow you to continue driving, but serious engine or misfire codes should be inspected as soon as possible.