Car Scan Tools

OBD2 Scanners: What Are They and What Do They Do?

Reading Time: 11 minutes

Discover how to unlock the secrets of your car with an OBD2 reader.

We all dread seeing the check engine light on the dashboard turn on. It means something’s wrong with the car. It doesn’t tell us exactly what, only that we’re going to have some work ahead of us to diagnose and repair it. This is especially troublesome in states that do car inspections, because your car may not pass and be illegal to drive until you fix the problem.

An OBD2 scanner can give you more insight into what problem is causing your check engine light. It’s also a useful diagnostic tool for monitoring your engine’s performance in real time. You may even be able to customize your car’s settings, features, and performance with the right hardware and software. 

In this guide, we’ll explain what OBD2 is, what a scanner is, how it works, and how to use one. We’ll also talk about what you should look for when choosing which scanner is right for you, whether an OBD2 scanner can actually fix your car or not, and which is the best scanner for you.

What Is OBD2?

OBD stands for On-Board Diagnostics. It’s a system that monitors the performance of your car’s engine and emissions systems, records data, and reports any problems it detects. 

OBD2 is the second version of this system for cars and trucks. Starting in 1996 for gas-powered vehicles and 2008 for diesels, it is a standard system that allows you to plug a scanner into any make or model of car to access the diagnostic information stored inside. It will work for any car from a Kia Rio to a Lamborghini Murcielago.

When the computer that runs the engine detects a problem, it will record a Diagnostic Trouble Code, also known as a DTC, in its memory. If the problem is severe enough, it will turn on the check engine light on your dashboard to tell you there’s a problem. At that point, it’s time to plug in an OBD2 scanner and investigate the issue.

Back when OBD2 first came out, it was a bane to DIYers. When you got a check engine light, you were then required to take your car to the shop to find out what it meant because dealers and shops were the only ones who could read those codes with their expensive diagnostic equipment. The market saw a need, though, and soon filled it with affordable OBD2 readers for the home hobbyist. Now, anyone can read trouble codes, clear the check engine light, and continue to maintain their car themselves.

What Is an OBD2 Scanner?

The device you plug into your car’s OBD2 port to read its trouble codes and live data is generally known as a scanner. These take many forms, ranging from a tiny box barely bigger than the OBD2 port itself, to a large device connected to the port by a wire. 

In locations that test your car’s emissions system, the computer that plugs into your car, communicates with the state’s auto registration database, and prints your new inspection sticker is also a type of OBD2 scanner.

Car Code Reader vs. OBD2 Scan Tool

Some people differentiate between an OBD2 “code reader” and “scan tool.” In this case, a code reader is a simple device that plugs in, displays trouble code information, lets you reset the check engine light, and not much else. This is the type of device that some auto parts stores will plug in and use to read your codes for free.

A scan tool provides far greater access to the car’s diagnostic data, systems, and features. Originally designed for professional mechanics, many consumer grade OBD2 scanners, such as FIXD, also fall into this category. These tools offer additional features like the ability to monitor live data. FIXD Premium also offers repair cost estimates, maintenance schedules and tracking, and more. 

There are many levels of scan tools available, ranging from FIXD, which is affordable and easy for anyone to use, to professional scan tools that are much more powerful, as well as much more expensive. While a code reader can read the extensive list of standard OBD2 codes, many manufacturers add codes that are unique to their vehicles, which a simple code reader may not be able to see. Scan tools can access more than just engine sensors and controls, including automatic transmissions, the anti-lock braking system, and more. 

It’s even possible for a professional scan tool to manually activate and deactivate systems on command for diagnostic purposes. For example, a mechanic friend of mine recently worked on a Toyota Prius where the fan that cools the hybrid battery wasn’t working. Using his professional scan tool, he was able to command the fan to turn on, regardless of whether it needed to or not, for diagnosis purposes. Furthermore, after turning the fan on, his scan tool told him the fan speed was 0 RPM, meaning that despite having power the fan wasn’t turning at all. This helped him diagnose some corroded fan wiring in this particular car.

How Does An OBD2 Scanner Work?

A scanner plugs into your car’s OBD2 port (typically located beneath the dash on the driver’s side) and connects to the computer that runs your engine and other systems. This computer is known as the ECU or ECM (engine control module)

With the ignition on, the car scanner can read and clear diagnostic trouble codes, reset the check engine light, monitor engine and sensor data in real time, customize features of your car, and more.

Wired (Handheld) OBD2 Scanners

A wired, or handheld, OBD2 scanner holds all of its functionality in the scanner itself, which plugs directly into the car’s OBD2 port. This is how the OBD2 system was originally designed to work with the dealer’s big expensive diagnostic systems. It still functions well, but the scanner can only do what the manufacturer designed it to do. These typically can’t be upgraded with new software to expand functionality.

The professional scanners that mechanics use typically connect to your car with a wire. The can do practically anything that OBD2 will let them. They can cost thousands of dollars, pricing it far out of range for the home hobbyist. This is why a shop may charge a $100+ diagnostic fee just to plug in their scan tool. They’re trying to make back their massive investment in this tool.

There are a few exceptions, however. Volkswagen, for example, has a system they call VAG-COM. It uses the standard OBD2 interface, but adds countless additional sensors and features to the basic OBD2 system. These are typically only accessible to dealers, but a serious Volkswagen or Audi owner can buy or build a special VAG-COM cable to connect to a Windows PC, and run a program called VCDS to gain access to all of this extra proprietary functionality. Home hobbyists can use VCDS to read proprietary trouble codes, modify door locking behavior, code a new key to work with the car, and more.

Some tuning companies, such as Cobb Tuning, supply a wired device that not only reads and clears OBD2 codes, but that also contains a variety of performance software tunes for your engine. While they work best in conjunction with an upgraded intake, exhaust, and other modifications, my Subaru WRX’s performance still improved dramatically with just the upgraded tune and original intake and exhaust. New tunes, either from Cobb Tuning or independent tuning shops, can be downloaded to the Accessport from your computer, then programmed into your car.

Wireless OBD2 Scanners

Wireless scanners use Bluetooth or WiFi to connect to your Android or iOS device. These let you run a multitude of apps that enable you to do far more than a basic scanner. For example, the FIXD scanner and app work together to not only monitor trouble codes, but also to provide information on how to make repairs, monitor your maintenance schedule, and predict future problems with your vehicle. Other apps let you modify some of your car’s features, such as how long the interior light stays on after you close the door, or whether the horn honks when you use your remote locks. 

When it comes to home use, a wireless scanner and an app on your phone are usually the best way to go, especially since you probably already have a smartphone.

How Do I Use an OBD2 Scanner?

Every 1996 or newer gas vehicle, as well as 2008 and newer diesel vehicles, has an OBD2 port located somewhere below the dashboard near the steering wheel. You can use the FIXD compatibility quiz to find out if your car is compatible with an OBD2 scanner like FIXD. Next, use the FIXD OBD2 port finder to look up the exact location for your specific vehicle.

Plug the FIXD OBD2 scanner into your car’s OBD2 port, usually located on the driver’s side under the dash.

Plug your scanner into this port, then start your engine. A wired OBD2 scanner will turn on and begin communicating with your car automatically. For a wireless scanner, you’ll need an app for your iPhone or Android that will pair with the scanner. An app such as FIXD handles this process for you with little work on your part. Other apps may require you to manually connect your phone to the scanner’s Bluetooth or WiFi connection.

How to Connect an OBD2 Scanner to Android

Android users should use a Bluetooth wireless scanner. Once configured, it will connect automatically and give your apps no trouble communicating with your car.

How to Connect an OBD2 Scanner to iPhone

iPhone users, however, often report that they are unable to use a Bluetooth scanner with their device. The common workaround for them is to use a scanner that uses WiFi instead of Bluetooth. You will need to manually connect to your scanner’s WiFi network. This also means that you will not be able to connect to your home WiFi network while you are connected to your car. One exception to this is the FIXD scanner and app, which works with Bluetooth and an iPhone with no trouble.

Once connected, the wired scanner or wireless app should present a menu of options to let you read codes, clear codes, and perform other functions depending on the device or app you are using.

What Should I Look For When Choosing an OBD2 Scanner?

The answer to this question depends on how you intend to use your scanner. Ask yourself these questions to make that decision.

What information do you want from it?

A simple $20 scanner and app will not provide the professional mechanic with the tools or information they need. Similarly, a professional scan tool will be too expensive for the average driver, as well as offer a great deal of functionality you don’t actually need.

The average driver and DIYer pretty much just needs a device that can read and clear trouble codes. Something that lets you view live data can also be handy for diagnostics, like figuring out if an oxygen sensor is good or bad. The FIXD scanner and app is a great solution for the everyday driver who wants information they can trust about what’s wrong with their car and what they should do about it.

Maybe you’re a “power user” who wants more than that. In the past, I’ve used an app to set up a virtual “dashboard” for track days that displays my oil pressure and oil temperature data on the screen in real time. These are two important parameters to monitor during sustained hard driving to make sure you don’t overheat or run out of oil, but most car dashboards don’t include these gauges. I was able to add them with an inexpensive wireless scanner and a third-party app to display this data while I put down laps on the race track.

Perhaps you want to customize the car itself. A tool like the Cobb Accessport is great for that, as well as standard OBD2 diagnostics, if Cobb makes a model for your particular car. If comfort and convenience is all you’re interested in, there are apps for that too. Carly is a tool designed specifically for customizing your car’s features, such as how long the interior lights stay on after you close the door, or whether the car beeps or not when you use the remote locks.  If you’re a VW or Audi driver, consider using the VCDS Windows software to access those unique Volkswagen features. 

Basic Diagnostics
  • BAFX (Requires third-party OBD2 app)
  • ELM327 (Requires third-party OBD2 app)
Advanced Diagnostics and Maintenance Tracking
  • FIXD Sensor and OBD2 app
Customizing Your Car
  • Carly
  • VCDS (VW and Audi only)
Performance Tuning
  • Cobb Accessport

How much do you want to spend?

There are plenty of affordable, quality OBD2 scanners under $100 for everyday drivers. The least expensive OBD2 scanner solution is a simple ELM327 wireless scanner and a third-party app. You can buy both of these for under $20 combined. You’ll need to configure these to work together and connect to your car, which can be a little tricky sometimes. But if you’re handy with technology, this is a cheap, effective way to read and reset your car’s trouble codes.

For a few dollars more — $59, to be exact — the FIXD OBD2 scanner and app is an all-in-one solution that’s extremely easy to use. Just plug in the scanner, install the free app, follow the instructions, and it just works. Not only does it explain what trouble codes mean in plain English, it also uses that same data to help you maintain your vehicle properly and avoid problems in the future.

Professional Car Scan Tools

Other types of code readers include tuners like the Cobb Accessport. It will read and reset trouble codes, but its primary purpose is to tune your car for better performance. The model I used to tune my Subaru WRX currently costs $675. Keep in mind, though, that what you’re really paying for is Cobb’s custom engine tune software and the means to easily install it in your car, rather than a simple code reader.

Professional scan tools are by far the most powerful devices available, but also too expensive for the average DIYer. The Snap-On Zeus, for example, provides intelligent diagnostics and pretty much everything the professional mechanic needs. It also costs $11,695, more than many used cars. When a pro is using it every day, such a tool will more than pay for itself. Unless you’re a pro, however, such a tool won’t be worth the massive investment.

Will an OBD2 Scanner Fix My Car?

No. It’s called a scanner because it will only scan the data in your car’s computer. It will not fix the problems it detects for you. It clear those codes and allow you to reset the check engine light, but that’s not the same as fixing the problems that caused it to turn on in the first place. If you don’t fix the problem that caused it to turn on in the first place, the light will just turn back on again when the car’s computer detects it’s still there.

While a scanner won’t fix your car by itself, it’s a useful diagnostic tool that will help you or your mechanic figure out exactly what’s wrong with your car and fix it intelligently, rather than just throwing parts at the problem, which can get expensive.

What is the best OBD2 scanner?

Every driver is different and which OBD2 scanner is best for you truly depends on your needs. To find the features that are the right fit for you, check out our list of the top 10 best OBD2 scanners.

While we may be a tad bit biased, for the average driver and car enthusiast, the FIXD OBD2 scanner is both powerful and extremely easy to use. Just plug in the scanner, install the free app, follow the instructions, and it just works. The data display inside the free FIXD app is much more user-friendly than other scan tools. It features a mix of text and visual data, including charts and graphs, that make it easy to understand what’s going on inside your vehicle.

FIXD OBD2 app shows you check engine code readouts, live OBD2 data, and more

It not only reads most engine codes but also translates them into plain English so that anyone can understand what they mean. If you have a trouble code, FIXD gives you a list of possible fixes for and links to in-depth OBD2 code descriptions and DIY videos to help you fix simple issues yourself. 

FIXD is far more than just a trouble code, reader, though. It also has Automated Maintenance Alerts so you never forget an oil or filter change. Multi-Vehicle Health Monitoring lets you connect multiple FIXD Sensors to every car you own and monitor their health in real-time from your smartphone.

Best of all, it’s affordable enough for anyone to buy and easy enough for anyone to use to better understand and care for their car.

Conclusion

The OBD2 scanners available today are capable of far more than the limited professional use originally intended. Anyone with a smartphone can now access much of the same data as a shop with a much more affordable scanner. Tools like the FIXD OBD2 scanner not only read diagnostic data but also translate the technical codes and jargon into plain English that anyone can understand, as well as display data in real time. Customization options ranging from turning on the interior lights to increasing engine horsepower are possible through what used to be just a diagnostic port. Sometimes technology really does make our lives easier.

Justin-Hughes

Recovering autocross and track day enthusiast. Once turned a VW Jetta into a pickup truck. Lives in a van down by the river. Dream car: 2001 Subaru WRC rally car.

Justin Hughes
Recovering autocross and track day enthusiast. Once turned a VW Jetta into a pickup truck. Lives in a van down by the river. Dream car: 2001 Subaru WRC rally car.

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    2 Comments

    1. […] nothing else, an OBD2 scanner needs to be able to read most engine fault codes and reset the check engine light. This feature […]

    2. […] this step, you’ll need an OBD2 scanner like FIXD. Simply plug the scanner into your OBD2 port usually located beneath the dash and scan […]

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