Want to know what’s really going on under your car’s hood?
An OBD2 (on-board diagnostics II) scanner is a powerful tool that helps you (or your mechanic) spot problems early — before they turn into costly repairs.
It connects to your car’s onboard computer through the Diagnostic Link Connector (DLC) using a wired, WiFi, or Bluetooth connection. This gives you access to most diagnostic trouble codes your vehicle generates.
But the question is, how to use an OBD2 scanner?
In this guide, we’ll explain each step and share practical tips to help you get the most out of your OBD2 scanner.
This Article Contains:
- How to Use an OBD2 Scanner Step-By-Step
- 7 Smart Ways to Get the Most Out of Your OBD2 Scanner
- 5 FAQs on How to Use an OBD2 Scanner
How to Use an OBD2 Scanner Step-By-Step
Running diagnostics on an OBD2 car scanner is simple.
Here’s a step-by-step guide:
Step 1: Locate the Diagnostic Link Connector (OBD Port)
Any car manufactured after 1996 features a Diagnostic Link Connector or OBD2 port. This 16-pin OBD II port is typically found on the left side of the driver’s dashboard underneath the steering column, usually covered with a door or flap.
If you can’t find the OBD2 port, check your scanner’s manual. All OBD2-compliant vehicles should have this port.
Step 2: Connect Your OBD2 Code Reader or Scanner to the DLC
After locating the DLC, make sure your car is turned off.
Plug the end of the OBD adapter into the DLC. If you own a Bluetooth OBD2 scanner, directly insert the Bluetooth adapter into the OBD2 port and link it to the necessary mobile OBD2 app to read engine codes.
Next, check the specific instructions on keeping the car in ON or idle mode after connecting to the DLC. This step is important because following the wrong method can damage the scan tool.
Following specific instructions allows your diagnostic scanner to communicate with the car’s computer and read the fault code. Confirm the wired connection to your OBD2 system by checking for a message on your OBD II scanner.
Step 3: Enter the Information Requested on the Scanner Screen
Your car has a Vehicle Identification Number (VIN). Depending on your car diagnostic scanner, you’ll have to enter the VIN before it can generate any OBD code.
The code scanner may also request other details like your engine and model type.
Where can you find the VIN?
It’s typically found on a sticker in the lower corner of the windshield on the driver’s side. Other places include under the hood next to the latch and at the front end of the vehicle frame.
Step 4: Access the Scanner Menu for OBD Codes
Once the car diagnostic scanner powers on, go to the main menu and select the vehicle system you want to scan. This will display any active or pending diagnostic trouble codes (DTCs).
What’s the difference?
- Active codes trigger the check engine light.
- Pending codes indicate a developing issue — often related to emissions — that hasn’t occurred consistently enough to trigger a warning yet.
Most scanners also offer additional scanner menu options, such as:
- Read codes: Shows current and stored DTCs, sometimes with brief descriptions.
- Erase codes: Clears codes and turns off the check engine light (usually with a confirmation prompt).
- Live data: Displays real-time sensor readings to help spot performance issues.
- Freeze frame: Captures key system data from when a code was triggered.
- Vehicle info: Includes the VIN and other system details.
- Inspection and Maintenance (I/M) readiness: Tells you if your emissions systems are ready for inspection.
NOTE: Basic scanners use physical buttons, while a Wi-Fi or Bluetooth scanner relies on app-based controls. Additionally, some scanners only display basic codes, while others let you explore specific systems and view detailed live data.
Step 5: Identify and Understand the OBD Codes
With the car diagnostics codes displayed, it’s time for you to interpret them. Each OBD code begins with a letter followed by four digits.
The letter in the diagnostic trouble code can be:
- P (Powertrain): Indicates issues with the engine, transmission, ignition, emissions, and fuel system
- B (Body): Indicate issues with airbags, power steering, and seatbelts
- C (Chassis): Implies issues with axles, brake fluid, and anti-lock braking system
- U (Undefined): Highlights issues that don’t fall under the P, B, and C categories
Now, let’s break down the meaning of the four-digit code that follows the letter:
- The first digit (after the letter) shows whether it’s a generic (0) or manufacturer-specific (1) code.
- The second digit points to the system involved:
- 1 = Fuel and air metering
- 2 = Fuel and air metering (injector circuits)
- 3 = Ignition system or misfire
- 4 = Auxiliary emission controls
- 5 = Vehicle speed or idle control system
- 7-9 = Transmission-related faults
- A-C = Hybrid system faults
- The last two digits narrow down the specific component or fault.
So a code, lets say P0301, breaks down as:
- P = Powertrain system
- 0 = Generic code
- 3 = Ignition/misfire
- 01 = Cylinder #1 misfire
Note down the codes displayed by the scanner and turn off your car. Then, carefully unplug the OBD II scan tool. If your scanner supports it, you can also transfer the diagnostic information to your laptop via USB or Bluetooth.
Some scanners briefly describe the fault, while others only display the code. In that case, you may need to look it up manually or use a companion app from the app store. If you can’t access or understand the live data, it’s best to consult a mechanic.
Step 6: Move on to Trouble Code Diagnosis
The OBD scanner or code reader tells you what’s wrong with your car, but it can’t tell you how to fix the problem. So, you’ll need to figure out if the error code implies a minor issue or not.
In either case, it’s best to take your vehicle to a certified mechanic’s shop to avoid expensive mistakes.
Step 7: Reset the Check Engine Light
Once you’ve fixed your car’s issues, the check engine light should turn off. But you can always use your OBD II scan tool to clear codes immediately.
How?
Go to the main menu of your OBD2 reader and find the check engine light option. Then, press the reset button. Give it a few seconds or minutes, and the engine light should turn off.
NOTE: You can use the ODB2 scan tool to erase an error code and stop the check engine light from lighting up temporarily if the issue isn’t fixed. However, the check engine light will illuminate again since the problem still exists.
Now that you know how to use your OBD2 scanner, let’s explore a few practical tips to really make it work for you.
7 Smart Ways to Get the Most Out of Your OBD2 Scanner
Your OBD2 scanner can do more than just read codes. With the right know-how, it becomes a powerful tool for diagnosing and maintaining your vehicle.
Here are eight ways to unlock its full potential:
- Run regular checks: Use your scanner during routine maintenance to catch issues early and avoid costly repairs.
- Keep it updated: Regularly update your scanner’s software to ensure it works with the latest vehicle models.
- Refer to manuals: Follow your vehicle’s manual and the scanner’s manual for advanced diagnostics and troubleshooting.
- Log and track codes over time: Save or export diagnostic data to spot recurring issues and trends, which is especially useful for older vehicles.
- Explore advanced features: Take advantage of functions like live data, freeze frame readings, and readiness monitors to get a more detailed view of your vehicle’s performance.
- Check emissions readiness: Use the “I/M Readiness” feature to see if your car is prepared for a smog test and avoid unnecessary test failures.
- Start diagnoses at home: A quick scan when your check engine light comes on can help identify the issue and save on car diagnostics fees.
NOTE: While an OBD2 scanner is a valuable tool for identifying potential issues and saving on vehicle diagnostics, it has its limits. For more complex problems, deeper inspection, or safety-related repairs, it’s best to rely on a professional mechanic who can interpret the data and make the right fix.
Got a few more questions?
We’ve got you covered.
5 FAQs on How to Use an OBD2 Scanner
Here are some common OBD II scanner-related questions and their answers:
1. Do You Need to Turn on the Engine When Using an OBD Scanner?
No, you don’t need to start the engine to use an OBD2 scanner. In most cases, turning the ignition to the “ON” position (without starting the engine) is enough to read and clear codes.
However, for functions like live data or performance monitoring, the engine needs to be running.
2. When Should You Use an ODB2 Scanner?
Here are a few situations where the scanner comes in handy:
- When the check engine light comes on, whether flashing or steady
- If you’re experiencing performance issues like rough idling, poor acceleration, or unusual fuel consumption
- To check I/M readiness before a smog or emissions test
- As part of routine maintenance, especially before road trips
- To check for any hidden or recently cleared diagnostic codes after purchasing a used car.
All in all, using your scanner regularly can help you catch issues early and avoid costly repairs down the line.
3. What’s the Difference Between an OBD1 and OBD2 Scanner?
The OBD2 device or scan tool uses OBD2 technology and is more advanced than the OBD1 scanner.
Here’s how they compare:
- Technology: OBD1 scanners use manufacturer-specific protocols and limited features. OBD2 scanners follow a standardized system (OBD II), offering broader compatibility and more detailed vehicle diagnostics.
- Connectivity: OBD1 scanners typically require a physical cable connection. An OBD2 scan tool can connect via cable, Bluetooth, or WiFi and display diagnostic information through a mobile app.
- Vehicle compatibility: OBD1 scanners work with vehicles made in or before 1995. OBD2 scanners are compatible with cars built in 1996 or later that support the OBD II system.
4. What Are the Different OBD II Scanner Types?
There are several OBD2 diagnostic code readers available, but they’re primarily categorized into two types:
- Code reader: An OBD2 code reader is a basic and affordable device that lets you read and clear generic fault codes. However, it has limited functionality and usually can’t access advanced diagnostic codes or manufacturer-specific codes.
- Scan tool: A more advanced (and more expensive) diagnostic tool. It not only reads and clears codes but also provides live data, freeze frame info, and access to manufacturer-specific systems for deeper diagnostics. Some car scanners may even have diagnostic equipment like multimeters or scopes.
5. What Should You Consider While Buying an OBD2 Scanner?
When purchasing a car diagnostic tool like an OBD2 scanner:
- Look for an OBD II scanner with the latest technology for compatibility with your future vehicles.
- Choose an OBD 2 scanner that’s user-friendly.
- Ensure the scanner size is easy for you to hold.
- Make sure it works with supported OBD adapters for greater flexibility in connectivity and functionality.
Clear the Codes, Clear the Road Ahead
An OBD2 scanner tool is for everyone. Whether it’s a built-in, handheld, or Bluetooth scanner, it’s an easy, affordable way to spot car issues.
The tricky part? Fixing what your scanner tool finds.
Fortunately, that’s where AutoNation Mobile Service comes in. Our certified mechanics come to you, interpret the codes, and handle the repairs — no shop visit needed. Plus, every service is backed by a 12-month/12,000-mile warranty for peace of mind.
We’re available seven days a week, and booking is simple. Just tell us what your scanner detected — we’ll take it from there.
Book online with us today.