Every car made after 1996 features a Diagnostic Link Connector (DLC). This 16-pin connector is typically located on the left side of the driver’s dashboard, near the steering column. There is often a door or flap that covers the connector. When in doubt, the owner’s manual will indicate the exact location of the DLC in your vehicle. 

Plug the end of the OBD2 scan tool into the DLC with the car turned off. Next, put the car in idle mode without turning on the engine. This will trigger communication between the DLC and the scanner. You should see a message that indicates the information is being transmitted or a connection is being established.

Every vehicle has an identification number (VIN). Some scanner models ask you to enter the VIN before it provides codes. If this is required, you can usually find the VIN on a sticker near the driver’s door. Next, make your way to the menu screen. The menu allows you to pick between the different systems in the car. 

When you select a system, the scanner will display both active codes and pending codes. Active codes are those that trigger the check engine light. Pending codes indicate the failure of an emission control system. Repeated pending codes can turn into active codes when the same issue occurs two consecutive times.

As you work your way through the codes, it’s important to understand the different letters and numbers displayed. Every code will start with a letter followed by a series of numbers. The lead letter will be one of the following:

• P: Powertrain - The engine, transmission, ignition, emissions and fuel system are all included in this category.
• B: Body - This can include airbags, power steering and seatbelts.
• C: Chassis - Axels, brake fluid and anti-lock braking system (ABS) are a few of the systems included under the chassis code.
• U: Undefined - Anything that doesn’t fall under the categories above.

After the letter, you’ll see a series of numbers. The scanner may show a single code or a number of codes. Once the codes are displayed, write them down, turn off the car and unplug the scanner. For help understanding how to read live data from OBD2 scanners, refer to the user manual. It should identify the different codes and what they mean. 

The fact that a code shows up doesn’t necessarily mean an immediate repair is needed. Research the individual codes thoroughly before jumping into repairs. When in doubt, take the vehicle to an Automotive Service Excellence (ASE) Certified Master Technician, and make sure they have their L1 Advanced Engine Performance Diagnostic certification.

OBD2 scanners are just one of the many auto diagnostic and testing tools available for at-home use. Investing in some basic shop equipment can help you tackle regular maintenance tasks and basic automotive repairs at home.

As with any device, make sure to refer to the owner’s manual for specific instructions on how to navigate the menu and codes on that particular model. Although the tools are all very similar, buttons and readings may vary slightly from one unit to another. 

Once you’ve learned how to use an OBD2 scanner, expand your knowledge by learning how to perform basic maintenance at home. Giving your own vehicle an oil change and replacing the air filter are great ways to save on costly repairs.