Over the past several decades, computer chips and control electronics have become as essential to motor vehicles' efficient, reliable operation as any mechanicals. An ever-growing list of a car's mechanical systems - be it the engine and transmission, brakes, suspension, emission controls, safety features, accessories and even the tires - is managed by an increasingly complex network of electronic controls and electrical sensors.
That's where onboard diagnostics come in, and why an OBD2 scanner has become a key tool to understand, maintain and repair modern vehicles. Do-it-yourself types, or anyone who wants to stay on top of what's going on inside their vehicle, can put an OBD2 code reader to good use. An OBD2 reader can certainly be useful for saving a few bucks.
It's equally clear that choosing an OBD2 diagnostic scan tool can be intimidating, and that's why we've assembled this list. There are hundreds if not a thousand scanners out there in auto parts stores, discount stores and at the far fringes of the internet, with prices varying by literally thousands of dollars. Many are excellent, regardless of price. Many are junk, with nothing like legitimate product support. Our best list includes the right OBD2 scanner tool for every purpose and buyer, and we'll update it periodically. Stay tuned afterwards for an overview of how scanners work, what they can do, our methodology for choosing them, key things to consider before purchasing and some pro tips.
This compact OBD2 scanner is conventional in that it connects to a vehicle's OBD2 port with a cable. With four keys and a simple menu, the Ancel BD310 delivers the basic functions every scan tool should. It also has a handy dash-vent attachment for easy, safe display while driving, and it can present a range of live operating data-temperatures, fuel use, spark advance and more while the vehicle is under load.
The "hybrid" part comes when you pair the BD310 scan tool to a smartphone via Bluetooth, then switch to operating it with Ancel's app for Apple or Android. With the graphics capability of your smartphone, the BD offers even more data presented in various forms, including gauges and graphs. It can also record familiar trip-computer functions like average speed, time and fuel consumption. It offers strengths inherent to both dedicated OBD2 scanners and Bluetooth dongles in a single device.
Ancel builds a wide variety of automotive diagnostic equipment. Its BD310 OBD2 scanner is loaded with useful functions at a really reasonable price.
Anself sells a strange range of hundreds of products, from telescopic back scratchers to inexpensive condenser microphones to 60-watt solar panels to yoga balls straight outta China. Its OBD2 to USB cable is one of them.
Sound dicey? Maybe it is, but here's what you get for your fourteen bucks: The cable, a manual and a CD with software that can turn your Windows laptop into an OBD2 scanner. The manual is not always easy to understand, but you can glean chunks of useful information. At the very least you can probably leverage the cable to run more familiar apps like Torque Pro for PC on your laptop, and that could provide most of the functions expected in an OBD2 scan tool and more.
The point? Twofold. First, devices like the Anself OBD2 to USB cable demonstrate what a Wild West scene the OBD2 scanner market can be. You can go with an established product, play it safe and spend more, and probably get what you pay for (including, with the right brands, good support). Or you can roll the dice and try some of the really cheap stuff that's out there on the web.
We're reasonably sure you could get the Anself OBD2 to USB cable to work to read a lot of the check engine light codes a vehicle generates, and clear them, and maybe even learn a bit more about what's going on in the car. The consequences of failure probably aren't catastrophic. The likely worst case is that you throw in the towel and bring your vehicle to a local auto parts store for a free code read. Again.
Is the potential upside worth $14? Are you feeling lucky today?
OBD2 car scanners 101
If this "onboard diagnostics" stuff sounds intimidating, the basics are actually fairly simple. It started in the 1990s, when the US government mandated that all vehicles beginning with the 1996 model year be equipped with a standard self-diagnostic system called OBD2 (for onboard diagnostics, generation 2), primarily to monitor emissions control systems. Since then, OBD2 has grown ever more sophisticated, monitoring ever more systems, but the process remains the same. When OBD2 records a problem, it creates a fault or diagnostic trouble code, then lights a warning on the vehicle dash (often that ubiquitous check engine light).
Fundamentally, an ODB2 scan tool reads and reports those trouble codes. It plugs into the car's diagnostic block, often called the OBD2 port - an easy-to-identify, trapezoid-shaped female connector, noted in the owner's manual and typically located under the dash or near the steering column. Then it scans the OBD2 system to find the faults or trouble codes.
Now, those codes are in fact codes, or five-place alphanumeric designations. Code P0420, for example, means the catalytic converter is not operating properly. The most rudimentary OBD2 scanners still simply report the error code, and you will have to check a reference manual or head for the internet to learn what P0420 means. But in 2020, the right, still modestly priced OBD2 scanner will tell you what the code definition is in English (or multiple languages) without having to look it up.
All OBD2 scanners should be able to clear the code, though the check engine light will likely flash again within a few miles if the actual problem generating the code hasn't been fixed. And there are a lot of codes - upwards of 5,000 and more all the time, according to experts. Roughly 60% of those check engine codes are generic or universal, meaning they're the same for all vehicles. P0420 means "catalytic converter not operating properly" no matter the brand or vehicle. Then there are a few thousand more codes specific to the vehicle manufacturer (such as Chevy, Ford or Toyota, and only Chevy, Ford or Toyota). A better OBD2 code reader will read the manufacturer codes, too, and explain those in English.
There's much more a good OBD2 scanner can do with the data in your OBD2 system. Most will confirm the vehicle's VIN and show you a Freeze Frame, or a rundown of key data points in the car at the moment the check engine trouble code was triggered, to help pinpoint what caused the problem. Most will report Live Data - a potentially long list of data points like fluid temperatures, engine speed and load, fuel injection and spark rate, sensor operation and so on while the car is running. It's like the full set of gauges most cars no longer have, and then some, and another valuable diagnostic tool.
Many OBD2 scanners will conduct a simulated smog test, checking the same things a service shop will check before it signs off on a smog certificate, and give you a good idea if the car will pass or fail in its current condition. Some OBD2 scan tools allow you to evaluate the battery, alternator and ABS system. They'll save or print reports with potential causes and possible repairs. The best can send commands to a car's individual control modules and even turn them off and on. They let you make finite adjustments that the vehicle manufacturer allows in its control software and calibrate the tire pressure monitor system, or TPMS.
OBD2 scanners are less expensive than ever, but competition makes the supply side of the market wilder than ever. Anyone who has carefully shopped for a mattress will understand. There's a handful of established players, a bunch of upstarts and a vast expanse of noise. Even the respected companies will build essentially identical scanners with different model numbers and insignificant appearance changes to sell through different retailers (sometimes at different prices). Differences are sometimes hard to discern.
Depending on where you live and what you drive, a decent OBD2 scanner can pay for itself in relatively short order, if only through the fuel and time saved by avoiding trips to the local auto parts store for a free code read. OBD2 code readers don't have to be expensive, but every car hobbyist or do-it-yourselfer should probably have one in the tool kit.
How we came up with our list
The list of the best OBD2 scanners above runs the gamut from the least expensive way to check engine trouble codes on your vehicle to excellent car enthusiast-type devices to a probably-too-expensive, full-professional mega scan tools. We evaluated reports from testing labs and scanned user ratings at popular shopping sites. We interviewed (harassed) experts, including Luke Daley at Innova and Jim Fish at BlueDriver, and we applied personal experience.
Before you choose an OBD2 code reader, consider the following pointers. And before you click "Confirm Order," have a look at our pro tips below.
Two things to know before you buy an OBD2 scanner
1. Its primary purpose: What do you plan to do with an OBD2 scan tool? If you just want to know what that check engine idiot light in the dash is telling you, or you want to independently evaluate what a repair shop is reporting, and maybe turn the light off if it's lit for something like a loose gas cap or a replaced EGR valve, you don't need to spend much. Some $60-$80 will get you where you want to go, reliably and repeatedly. Even when the problem is solved, a basic OBD2 scanner remains a valuable tool if you or someone you know is looking for an inexpensive used car.
If, on the other hand, you're an automotive enthusiast, a frequent do-it-yourself person or the friend nonenthusiasts come to for car advice, it's certainly worth spending more. More expensive scanners can have broader make and model coverage. An OBD2 code reader with the right features will help you look deeper into a car's control systems, troubleshoot problems and settle on appropriate repairs. A better one can help you analyze vehicle performance, optimize efficiency and better understand how a vehicle works.
Consumer-priced scanners today do things that were reserved for $5,000 pro-grade scanners just a couple of years ago. The best are good enough that, if you intend to make money fixing cars, you could use them to get started. Eventually, though, you're probably going to need one of those expensive pro-grade models.
2. Which type works for you: Across the price spectrum, there are basically two types of OBD2 scanner. The dedicated hand-held scan tool is a self-contained device that plugs into the OBD2 port via cable (preferably long enough to reach from inside the car to the engine bay) and does its job. It has its own screen, buttons, software and computer chip.
The second type is a Bluetooth OBD2 scanner, known in the trade as a Bluetooth dongle. This type is usually a fairly small, plastic device that plugs into the OBD2 port and then connects to a smartphone or tablet via Bluetooth. Its job is to wirelessly transmit data from the vehicle's OBD2 system to the phone, where that data is processed and presented by the dongle manufacturer's control app. With a Bluetooth OBD2 scanner, the quality of its manufacturer's software is paramount.
The primary advantage of the Bluetooth device, if it isn't obvious: lower cost. Why pay for a screen and computer chip when your smartphone already has those? A Bluetooth OBD2 code reader dongle uses those components on your phone, where the screen and the chip are probably much higher quality than you need for this task.
If the typical cost advantage in a Bluetooth OBD2 scanner sounds like a no-brainer, you should consider the more subtle issues. Dedicated scanners are in important respects more efficient to use, and if you use the code reader regularly to diagnose check engine lights, or for longer sessions, speed and simplicity matter. With a self-contained scanner, you never have to worry about the quality of the Bluetooth connection, your phone charge or the strength of your Wi-Fi or cellular signal (the typical Bluetooth OBD2 scanner relies on access to internet databases). You won't be interrupted by incoming calls or notifications while you're using it. A good dedicated scanner is more impact-impervious than a smartphone, and drops are probably inevitable. What happens if your $1,000 phone falls in the engine bay and lands on the transaxle case, or gets wedged between a manifold and the engine block? Many Bluetooth scanners want to sell you upgrade subscriptions, and some of the apps have ads.
You can get a solid, dedicated OBD2 scan tool for $100 or less, so the choice isn't as obvious as it might first appear. It probably goes back to the first thing you need to know when buying an OBD2 scanner: your primary purpose for doing so. And maybe how often you plan to use it.
Pro tips
The great majority of OBD2 scanners sold today will work on the great majority of vehicles built for model year 1996 and beyond. Yet for fairly arcane reasons, there are exceptions to this assumption of universal application (a few companies still build scanners for specific makes). Most reputable scan tool manufacturers have application checkers on their websites, so play it safe. When you think you know what scanner you want, check to ensure that it will work on cars you might regularly want to use it on. And if you plan to buy a Bluetooth-based scanner, there's another potentially embarrassing mistake. The control apps that connect with the OBD2 dongle are specific to the operating system on the phone, tablet or PC that's going to run the app. Some manufacturers have an app for Android or Apple, but not for other OSes, much less for Windows devices. Confirm that there's an app that will work on your device.
There's one more word of caution to note here. With some OBD2 scanners, some of the features or commands may not work on every make or model of automobile. This is largely a function of how the automakers build their control architecture or operating software. Some brands are just more particular about what they'll let people see, and who they'll let see it. This applies particularly with scanners that allow bidirectional control or adjustments within the vehicle's control software. As a rule of thumb, US automakers generally allow the most access. Higher-end European brands allow the least. Again, you can sometimes learn something using the application checker on manufacturer websites. Often you can find the OBD2 scanner's operating manual online, so look at that, too.
An OBD2 scanner is primarily intended to help figure out what might be wrong with a vehicle and then help get it fixed. It can reset certain parameters once the repairs are accomplished. More capable scanners can make finite adjustments in certain vehicle systems. An OBD2 scanner is not a flash programmer - a device that can actually rewrite the carmaker's control code in search of more horsepower from the engine or different transmission shift points. Flash programmers are a thing, but they're a different beast entirely, and typically auto-brand specific.
Finally, when it comes to OBD2 scanners, don't underestimate the value of product support. Even the most confident do-it-yourself folk will have questions about what the code reader might be telling them, or something that doesn't seem to be working as it should. Beyond limitations noted in the list, the manufacturers of our best scanners should be able to provide answers to your questions, and in reasonably short order.
Product support includes software updates. The reputable brands update their OBD2 scanner software regularly - at least once a year - so stay on top of it. The updates are usually easy to install, from a PC or over the air.
Written for Roadshow by J.P. Vettraino.