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Crash Course:

An OBD2 scanner is a device that reads your vehicle’s “check engine light” codes and performs emissions tests. Any car owner can learn how to use one.

A basic OBD2 scanner suitable for most users costs around $60.

Most OBD2 scanners are compatible with most vehicles, but if you have a rare imported or luxury vehicle, you may want to check before buying one.

You don’t need to be an auto repair expert to use an OBD2 scanner. Most of them are simple devices that perform two basic functions: 

Check engine fault codes

Run emissions diagnostics

By using an OBD2 scanner when your “check engine” light comes on, you may be able to identify the problem and find a possible solution. In some cases, you may even be able to fix the problem yourself without a trip to the mechanic. If you do need to take the car into the shop, you’ll go in with more knowledge and have the chance to shop around for a repair ahead of time.

Since most mechanic shops charge $100 or more to diagnose a vehicle problem, you can start saving money after just one use. Several of our best OBD2 scanners cost around $70 or less.

What Is An OBD2 Scanner?

An OBD2 (or OBDII) scanner is a device that plugs into a car’s onboard computer and presents you with information on how the vehicle is running. Virtually all of them will read onboard diagnostics trouble codes (DTCs).

More advanced (and expensive) scanners can perform more functions, including:

View live data about engine performance

View vehicle system information recorded at the time a DTC occurred

Run emissions tests

Check the status of critical systems such as the anti-lock braking system (ABS) and the supplemental restraint system (SRS)

Alter engine and fuel system parameters to optimize engine performance

Change advanced computer settings such as the speed that your vehicle’s locks automatically engage

With that data, you can decide whether there’s an urgent problem that needs to be addressed.

How To Use An OBD2 Scanner: Step-By-Step

Every OBD2 scanner is a little bit different, so it’s worth reading the user manual to learn specific information related to your car diagnostic tool. But the basic steps for operating most OBD2 scanners are the same.

Locate the ODB2 port

Connect your OBD2 scan tool

Turn your vehicle on

Initiate the DTC scan

Decipher the DTCs

1. Locate The ODB2 Port

OBD2 ports are typically located below and to the left of the steering column. Some are tucked back pretty far, so you may need to crouch down and use a flashlight to locate yours. The OBDII port is a 16-pin, trapezoid-shaped connector.

2. Connect Your OBD2 Scan Tool

There are both wired and wireless OBD2 scanners. If it’s wired, you’ll plug your device’s cord to the OBD2 port. If it’s wireless, there is typically a dongle that plugs into the port that communicates with your device.

3. Turn Your Vehicle On

Some OBD2 scanners are self-powered, while others require energy from your vehicle’s battery to operate. Check your owner’s manual to determine if you should power your vehicle to use your OBD2 scanner. In most cases, you’ll need to turn your car’s power on but keep the engine off to use an OBD2 scanner.

Many OBD2 scanners will automatically detect your vehicle information, but some may require you to enter this information yourself. You could be asked to simply input your vehicle’s year, make, and model, or you may need to provide your vehicle identification number (VIN). 

If you need to locate your VIN, it’s typically displayed on the driver’s side dashboard or a sticker inside the driver’s side door (you’ll need to open the door to see it).

4. Initiate The DTC scan

Your car scanner may automatically power on when the car is powered, or you may need to press a button. When everything is ready, locate the menu option to check diagnostic trouble codes or initiate a scan. Check your scanner’s user manual to find out how to do this if you’re having trouble. With most OBD2 scan tools, this feature shouldn’t be difficult to locate. Many have a single button that initiates DTC scans.

There are generally two types of DTC codes: active and pending. Some scanners have separate menu options for viewing each type of code.

Active codes are DTCs that trigger the check engine light. These represent issues that should be addressed immediately.

Some DTCs related to the emissions control system don’t immediately trigger the check engine light. These are minor but recurring failures and will be stored as pending codes. A pending code will become an active code and trigger the check engine light once a certain failure threshold is met.

If you’re trying to determine the cause of a check engine light, check active codes.

5. Interpret The DTCs

A diagnostic trouble code is displayed as a string of letters and numbers. For example, the engine trouble code for a loose gas cap is “P0457.” The quickest way to understand the meaning of a DTC is to look it up online using a search engine. Some more advanced diagnostic scanners will decipher and explain the code for you.

The first letter in a DTC can be P, B, C, or U. This letter indicates what part of your vehicle has an issue.

P: Indicates an issue with the powertrain (the engine, transmission, and fuel system)

B: Indicates an issue with the body (cabin interior parts such as the steering system, airbags, and seatbelts)

C: Indicates an issue with the chassis (components underneath the car such as the axles, ABS, wheels, and power steering)

U: Indicates a network issue (wiring)

Some diagnostic trouble codes are universal, while others are manufacturer-specific. The number that follows the first letter of a DTC will be either 0 or 1. A 0 indicates a universal (generic) code, and a 1 indicates a manufacturer-specific code.

Emissions Testing

In addition to checking DTCs, a DIY home mechanic can use an OBD2 scanner to perform an emissions test. To do so, follow steps one through three listed above. Once your diagnostic scan tool is powered, select the emissions test menu option instead of the DTC scan.

Which OBD2 Scanner Is The Best?

The best OBD2 scanner for you depends on your budget, specific needs, how many features you want, and how long you want it to last. Most OBD2 scanners are compatible with most car makes and models. However, your vehicle is vintage, luxury, or built by an obscure manufacturer, research which OBD2 scanners are compatible with it before buying one.

For those who want a basic OBD2 scan tool for DTC lookup and emissions tests, one of our recommendations is the Foxwell NT301. This scan tool costs about $70 and is very easy to use.

Another one of our picks is the BlueDriver Bluetooth Pro. The BlueDriver is a little more expensive at around $120. This Bluetooth OBD2 scanner pairs with your smartphone and offers more advanced features, such as custom engine monitoring and access to a repair report database.

If you want to compare the features between our top picks, check out our review of the best OBD2 scanners on the market today or our review of the best Bluetooth OBD2 scanners.

OBD2 Scanner Expert Advice

We’ve interviewed a variety of automotive experts about OBD2 scanners and other vehicle maintenance tools.

One of those experts, Zac Salerno, a technician at Import Performance and certified safety inspector with more than three years of experience recommended that car owners start with a basic-level OBD2 scanner before investing in something more advanced.

“It’ll read your codes, you’ll get an idea of what’s going on,” Salerno said. “And that’s the biggest part, is at least getting a jumping-off point to figure out where your diagnosis starts.”

Unless you are managing a large garage of vehicles, or servicing rare vehicles, a basic OBD2 scanner is sufficient for the average person.

OBD2 Scanner: FAQ

Below are some commonly asked questions about using an OBD2 scanner:

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Original article: How To Use An OBD2 Scanner