The last thing you want is for your car's "check engine" light to come on, especially during the cold winter months. But when that light does come in, knowing the cause can be a great relief and money saver.
The good news is that you don't have to take the vehicle to a mechanic to diagnose the problem. That's because with an onboard diagnostic (OBD 2) scanner you can figure out what's wrong with the car and then have it fixed.
There are two types of OBD 2 scanners: the handheld units that have a connection cable and screen as well as smaller units that plug into the car's OBD port and connect to a phone or tablet via Bluetooth. The best OBD 2 scanners we tested are small enough to fit in a glove box and were purchased from Amazon for less than $100.
Despite their low price, OBD 2 scanners can ferret out thousands of car problems, simple and complex. All of them work on cars made since 1996. We took dozens of OBD 2 devices on test-drives that included monitoring the car's dynamic data and introducing faults.
The best OBD2 scanners can turn off the check-engine light and, for example, distinguish a broken catalytic converter from a clogged EGR valve, potentially saving you hundreds of dollars, all without getting your hands dirty. We tested each ODB2 scanner and rated them based on features, setup, ease of use and – above all – value.
The best OBD 2 scanners
1. Ancel BD310
The best OBD 2 scanner for most people
Display/size: Color/2 inches | Size: 5.1 x 2.4 x 0.6-inches | Weight: 5.4 ounces | Bluetooth/Handheld: Yes/Yes | I/M Readiness test: Yes | Displays live data: Yes | Number of keys: 4 | Warranty: 3 years
The best OBD 2 scanner overall, Ancel's BD310 is just as good as a handheld scanner with a screen as it is when connected to a phone or tablet via Bluetooth. It can also augment the car's cockpit with a supplemental display. Think of it as freedom of scanning choice.
At 5.1 x 2.4 x 0.6 inches and 5.4 ounces, the BD310 is small, lightweight and will disappear into a car's glove box. It has an icon-based 2.0-inch color display, a 56-inch cable and a magnetic back for attaching to a car dashboard or its vent with the included bracket.
This makes it just as good for hanging over the hood looking for an engine problem as monitoring the engine while driving. The scanner can show an assortment of performance details, like coolant temperature, engine timing, engine speed and other live parameters, as numbers or graphs. It also offers a pre-inspection I/M Readiness test.
On the other hand, the BD310's rudimentary four-key interface can make navigation awkward. There's also a mode button on the side for selecting Bluetooth and cable operation.
This ODB scanner quickly connected with my 2014 Audi Allroad and displayed a graph of the engine speed along with other parameters. Later, it found my introduced fault and was able to turn off the car's check-engine light.
The Ancel BD310 includes a three-year warranty and can do so much more than single-purpose scanners.
2. Autel AutoLink AL539
A smart pick for checking your car for electrical problems
Display/size: Color/2.8 inches | Size: 6.7 x 3.6 x 1.4 ounces | Weight: 10.6-ounces | Bluetooth/Handheld: Yes/No | I/M Readiness test: Yes | Displays live data: Yes | Number of keys: 8 | Warranty: 1 year
Autel's AutoLink AL539 does something that most other OBD 2 scanners can't: It can check electrical connections with a built-in multimeter to uncover pesky electrical problems. Sadly, the multimeter is a stand-alone function that doesn't work when the AL539 is connected to the car as an OBD 2 scanner.
Despite its soft rubber bumpers, the AL539 is fairly compact and light at 6.7 x 3.6 x 1.4 inches and 10.6 ounces. It has a unique pull-out leg so the device can stand on its own, as well as a generous 58-inch cable.
The scanner's bright, 2.8-inch color display has icons for major functions and an easy-to-follow eight-key interface. Its pre-inspection readiness key has three lights that glow red (permanent fault), yellow (temporary fault) or green (no faults).
Below are connectors for the multimeter's included test cables, to check continuity, current and voltage. The device's lithium-ion battery powers it for checking fuses, the alternator's voltage or the gas gauge.
After 9 seconds, the AL539 was online with my 2014 Audi Allroad, displaying the engine speed, coolant temperature and other items. It found my introduced fault and turned off the check-engine light.
The AL539 includes a padded case, a one-year warranty and PC software. If you have electrical problems, this is one of the best OBD 2 scanners to get.
3. SeekOne SK860
A large color screen and a lifetime warranty
Display/size: Color/2.8 inches | Size: 7.8 x 3.8 x 1.2 inches | Weight: 11.2 ounces | Bluetooth/Handheld: No/Yes | I/M Readiness test: Yes | Displays live data: Yes | Number of keys: 8 | Warranty: Lifetime
Its large color screen, range of tasks, lifetime warranty and ease of use make the SeekOne SK860 a winner that stands apart from the OBD 2 crowd.
Although it can feel bulky and heavy, at 7.8 x 3.8 x 1.2 inches and 11.2 ounces, the SK860 has soft rubber bumpers and a rugged design. To ease connecting the scanner to your vehicle, it has a 58-inch cord. It also has a bright, 2.8-inch color display.
The eight-button navigation scheme and icon-based interface make it easier to use than some budget scanners. Its one-button I/M pre-inspection readiness key is augmented by its three-light fault-code indicator: Green means no fault codes, while yellow and red mean pending and permanent problem codes, respectively.
Able to work with generic codes as well as those of 43 manufacturers, from Ford to Fiat, the SK860 took 5 seconds to connect with my 2014 Audi Allroad. It immediately displayed my car's vehicle identification number (VIN) and examined the battery. It was able to show live data, like engine speed, oxygen sensor readings and coolant temperature. The scanner quickly found my introduced fault and turned off the check-engine light.
The SK860 does much more than typical handheld scanners, and comes with a padded case, lifetime warranty and code updates. In other words, it's as close to a professional tool as you can get these days.
4. Autophix Code Reader OM126
Lifetime software updates for an affordable price
Display/size: Color/2.4 inches | Size: 4.8 x 3.0x by 0.9 inches | Weight: 11.2 ounces | Bluetooth/Handheld: No/Yes | I/M Readiness test: Yes | Displays live data: Yes | Number of keys: 4 | Warranty: 3 years
Despite being among the most affordable OBD 2 scanners available, the Autophix Code Reader OM126 includes lifetime software updates, allowing it to keep up with technological and model changes. It could be the last scanner you get.
At 9 ounces and 4.8 x 3 x 0.9 inches, the OM126 is slightly larger and heavier than the Launch X431. The unit's bumpers give the scanner a rugged look and it feels good in the hand. Its bright orange color should make it easy to find in a crowded toolbox.
The OM126's 2.4-inch color screen shows six icons, but its four-key interface lacks right- and left-arrow keys, making navigation hard to figure out at first. Its I/M readiness test for checking the car's major components doesn't have dedicated colored LEDs but displays the results in an easy-to-read format.
In addition to displaying live engine parameters, like engine speed and coolant temperature, it can graph them for comparison. Able to report generic and manufacturer-specific codes, the scanner can display oxygen sensor and battery data.
The OM126 quickly showed that I had unplugged the oil temperature sensor on my Audi Allroad; it was able to turn off the check-engine light. Happily, the OM126 comes with a lifetime's worth of software. This makes the OM126 potentially the only OBD scanner you'll ever need to buy.
5. Autel MaxiAP AP200
A compact OBD 2 scanner designed to work with your phone
Display/size: Single LED | Size: 1.9 x 1.1 x 0.9 inches | Weight: 1.1 ounces | Bluetooth/Handheld: Yes/No | I/M Readiness test: Yes | Displays live data: Yes | Number of keys: N/A | Warranty: 1 year
Autel's MaxiAP AP200 works with phones and tablets, and its rubber grips make the 1.9 x 1.1 x 0.9-inch device easy to insert and remove from the car's OBD port. Small and light, it weighs 1.1 ounces and has a single LED.
After plugging the AP200 into the car's OBD port and selecting it in my tablet's Bluetooth interface, the scanner connected on the first try with no passcode needed. The MaxiAP apps for iOS and Android are easy to install and provide a window on car performance but they were clearly written for phones with a vertical orientation and half-screen resolution.
The screen shows fault codes, has an I/M readiness test and displays live data, like engine speed and coolant temperature. You can view the data as numbers, line graphs or realistic-looking automotive gauges.
Once connected, the AP200 had a 30-foot Bluetooth range. But the device can be frustrating because the scanner takes upward of 30 seconds to compile its data and 10 seconds to change tasks. It took about 10 seconds for it to detect my introduced fault. Able to turn off the check-engine light, the AP200 can export reports as Acrobat PDF documents.
The AP200 includes a 1-year warranty.And at $70, it is a good compromise between design and price tag.
6. BlueDriver Bluetooth Professional OBDII Scan Tool
A full-featured scanner that warns of recalls and makes repair suggestions
Display/size: Single LED/N/A | Size: 2.2 x 1.9 x 1.0 inches | Weight: 1.1 ounces | Bluetooth/Handheld: Yes/No | I/M Readiness test: Yes | Displays live data: Yes | Number of keys: N/A | Warranty: 1 year
At $99.95, the BlueDriver OBD2 kit is pricier than some other models. But it's worth every penny, because it goes beyond basic scanners to show dynamic data, warn of recalls and offer repair suggestions.
BlueDriver quickly detected my car's fault (which was a disconnected oil temperature sensor), erased it and turned off the check-engine light. This handy gadget also performs pre-inspection emissions checking and interprets the specialty codes for Detroit's Big Three automakers, BMW/Mini and Toyota vehicles; Nissan's codes are being added. It can count engine misfires on many newer cars, and reports can be saved as PDFs.
The BlueDriver had a 32-foot range, and its app is available for Android and iOS. Its Freeze Frame feature delivers a slice of data, and the app can display speed, engine RPMs and other data as numbers or graphic gauges. I liked the helpful videos, but the computer-synthesized voice was annoying.
It's no longer our top overall pick for OBD scanning, but the BlueDriver is so complete that it is still a great choice at under $100.
A small size makes it easy to connect this OBD 2 scanner
Display/size: 2 LEDs | Unit size/weight: 2.4 x 1.9 x 0.8 inches | Weight: 1.1 ounces | Bluetooth/Handheld: Yes/No | I/M Readiness test: Yes | Displays live data: Yes | Number of keys: N/A | Warranty: Lifetime
Don't let the DodyMPS's diminutive 2.4 x 1.9 x 0.8-inch size and 1.1-ounce weight fool you. It is a powerful and easy-to-connect car scanner that includes a lifetime warranty and software updates.
The black scanner has a small cutout with two LEDs and QR codes printed on its side for getting the needed Android and iOS apps. After downloading, installing and firing up the app, the software looked for the scanner and connected on the first try, making it one of the easiest OBD scanners to use.
DodyMPS shows your car's VIN code when it starts up and on many of its windows. On the downside, the app runs vertically at half resolution and was designed for use with a phone.
In addition to viewing my Audi Allroad’s fault codes and running a pre-inspection I/M readiness test, it showed live data, like coolant temperature and engine and car speed. It quickly found the car's fault that I created and was able to turn off the check-engine light.
Like the iCar Pro, the DodyMPS scanner costs $30, but the DodyMPS device goes the extra mile with a lifetime warranty and software updates for new models and technologies.
8. Nexpeak OBD2 NX501
Built tough with a bright color display
Display/size: Color/2.8 inches | Size: 7.6 x 3.8 x 1.3 inches | Weight: 1.6 pounds | Bluetooth/Handheld: No/Yes | I/M Readiness test: Yes | Displays live data: Yes | Number of keys: 8 | Warranty: 3 years
The Nexpeak NX501 OBD 2 scanner not only does the expected car checks but with lifetime software updates, it's a keeper.
With soft rubber bumpers, the NX501 is ruggedly built and comfortable to use. At 7.6 x 3.8 x 1.3 inches, it is on a par with Autel's AL539 but does without the AL539's electrical multimeter and pull-out leg.
The device has three LEDs for the I/M pre-inspection test: green (no faults), yellow (temporary problem) or red (permanent fault). In addition to examinations of the battery and oxygen sensor, the NX501 interprets generic and many manufacturer-specific fault codes. The device quickly noticed when I disconnected the oil temperature sensor on my Audi Allroad and turned off the car's check engine light.
At 2.8 inches, the NX501's Display is bright with colorful icons for different features, and it can show everything from engine speed to coolant temperature along with colorful fever graphs. The tool's eight-key navigation make it easy to move between scanning tasks.
The NX501 includes a padded case, lifetime software upgrades and one of the longest OBD cables at more than 5 feet. If you sign up for the company's Super User program, NexPeak extends it for another year and offers other goodies.
9. Konnwei KW850
A feature-rich scanner that's on the big side
Display/size: Color/2.8 inches | Size: 7.8 x x 3.8 x 1.2-inches | Weight: 11.2 ounces | Bluetooth/Handheld: No/Yes | I/M Readiness test: Yes | Displays live data: Yes | Number of keys: 8 | Warranty: 2-years
From its range of features to its price tag, the $70 Konnwei KW850 OBD 2 scanner bears a striking resemblance to the SeekOne SK860, making it a good choice for those who want professional results on a budget.
One of the most thorough and reliable scanners available, the KW850 has rugged rubber bumpers. But the device's size can be a handful to work with at 7.8 x 3.8 x 1.2 inches and 11.2 ounces. Its 2.8-inch icon-based color screen and eight-key interface are easy to figure out and get used to.
The KW850 has an I/M pre-inspection button that illuminates red for a permanent fault, yellow for a temporary fault and green for a clean test. It displays and graphs live engine data, like speed, timing and coolant temperature, as well as showing battery information.
Able to interpret generic and most manufacturer codes, the KW850 immediately discovered the oil temperature sensor I had disconnected on my Audi Allroad. I was able to turn off the check engine light.
With a padded case and extra-long 58-inch cable, the KW850 is well worth a look.
10. Foseal F0-01
A good cheap OBD 2 scanner, so long as you don't mind the short cable
Display/size: Color/2.8 inches | Size: 6.4 x 3.4 x 1.0 inches | Weight: 7.4 ounces | Bluetooth/Handheld: No/Yes | I/M Readiness test: Yes | Displays live data: Yes | Number of keys: 6 | Warranty: 2 years
At $30, Foseal's F0-01 is one of the cheapest handheld OBD 2 scanners with a color display you can get. It may not have all the bells and whistles of other devices, but it can be the equivalent of driving around with a mechanic in your glove box.
The F0-01 has a squared-off look with an inset for your thumb and grippy edges along the bottom that feel good in the hand and can help keep it from being dropped. Unfortunately, most will find its 30-inch cable too short.
At 6.4 x 3.4 x 1.0 inches and 7.4 ounces, the Foseal scanner is bigger than Ancel's OS601 but its vivid 2.8-inch color display more than makes up for it. Up front, the F0-01 has a six-button interface that, unfortunately, has only up, down, OK and go-back keys. Oddly, there are shortcut keys to the car's VIN number and fault codes, but no problem warning light.
In a few seconds, the F0-01 linked with my Audi Allroad and displayed live data as numbers or as line graphs. It found my introduced fault and turned off the check-engine light.
Foseal's F0-01 does a lot with a little and comes with a two-year warranty. As long as you don't mind the short cable, it could be the best $30 you can spend on your car.
How we test OBD 2 scanners
To check out these inexpensive OBD2 scanners, I used my 2014 Audi Allroad vehicle over several weeks of garage and on-the road use. After connecting each scanner to my car's OBD II port, I made sure they could report the car's VIN code. For the wireless scanners, I connected to my Apple iPad, Microsoft Surface or Samsung Galaxy S9+ phone via a Bluetooth or Wi-Fi connection. The handheld scanners needed only to be plugged in.
Next, I measured the cord's length on the handheld scanners and the wireless range on the others. With the car running, I monitored the engine and other vital systems, and then disconnected the engine's oil temperature sensor. Finally, I checked the details provided by the scanner, fixed the problem, turned off the check-engine light and erased the error code.
Then, I hit the road, to see if the scanner could display operating data, like engine speed, timing and coolant temperature.
OBD 2 101
Regardless of which OBD 2 scanner you use, you'll need to crack its code. All fault codes have four numbers and a letter prefix:
- Powertrain (P)
- Body (B)
- Chassis (C)
- Undefined (U)
Of the roughly 5,000 diagnostic fault codes available, some are generic and available to all cars, like air temperature and throttle position. For these, the numeric section starts with a 0. Others are specific to individual carmakers and represent either a special piece of hardware or a more in-depth analysis of the problem. These start with a 1.
For instance, if you get a P0098 code, chances are that there's something wrong with the engine's intake air temperature sensor. By contrast, a Ford that displays a P1112 specialty fault code means that the intake air temperature sensor is reporting values intermittently and should be replaced.