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Ever get the dreaded “Check Engine” light on your dashboard? Well, if you own a vehicle built after 1996, chances are you’ve dealt with this before. Check Engine Lights (CEL, or also known as the Service Engine Soon light and Malfunction Indicator Lamp (MIL)) are triggered by myriad onboard sensors that monitor vehicle health. In the mid-1990s, there were a few dozen sensors onboard, monitoring systems like braking, emissions control, engine electrics (spark plugs and engine timing) and safety systems like anti-lock braking. Computer Code Reader For Cars
Fast-forward to 2023, and there are hundreds of sensors onboard.
The health of your vehicle is monitored by a complex system dubbed “On Board Diagnostics,” which debuted in cars under the moniker OBD-I in 1991. With 1996 model year cars, a new system was developed called OBD-II (often abbreviated as OBD2) that utilizes a cabin mounted port to allow for OBD system readouts via a computer or specialized “scan tool,” designed to decipher the scores of potential issues your vehicle may have when the CEL is triggered.
The port’s design is standard across different automakers, it’s always located within 3 feet of the driver and can be accessed without tools.
Today, do-it-yourselfers have a large variety of OBD2 scanners they keep in their home garages, or even in their vehicles. A good scanner shows what’s wrong when the CEL comes on and allows users to clear the code, turning off the warning light.
CEL trouble codes also provide information useful for carrying out any repairs that might be necessary. If the underlying problem isn’t fixed the check engine light will come on again. Fuller-featured models can include Bluetooth connections to smartphones and tablets, a wider array of functions, databases of repair and parts information specific to the vehicle, the issues detected and more. Top of the line scanners may also have a database of manufacturer specific diagnostic tools.
The good news is that most of these more functional scanners are still reasonably priced as seen in our list.
You Maybe Interested In OBD2 Scanners Available On Amazon
Built-in OBD2 DTC lookup library
No battery or charger needed
Supports 9 protocols, 2.5 ft long cable, Clear display LCD screen
Clears check engine light, Monitor whole fleet from 1 account, Know vehicle history
Works on all OBD2 protocols, Read/Clear CEL, Fully ELM327 compliant
Compatible with EVs, Compatible with iOS & Android devices, Easy to use
Retrieve I/M Readiness status, Retrieve freeze frame data
On-screen DTC definition, Clears check engine light
No wires or batteries, Read/Clear CEL, Fully ELM327 compliant
The Autel AL539 hits the sweet spot when it comes to a blend of features, build quality and price. It’s compatible with any OBD2-equipped automobile, supports multiple languages and goes beyond check engine functions to include antilock braking systems, airbags, transmissions and more. The handheld unit has rugged construction and is surrounded by a rubberized casing that’s easy to grip. The AL539 also has a built-in multimeter for diagnosis of vehicle batteries, charging systems and electrical faults. There were a handful of complaints with this model. The biggest concerns are around defective units shipped (users exchanged them for good ones), firmware update failures and subpar customer service.
The BlueDriver Bluetooth Pro scanner is a simple, elegant solution to get vehicle codes (airbag, ABS, tire pressure monitoring and other vehicle systems). It’s one piece, which plugs into the OBD2 port. Retrieved data is sent via Bluetooth to smartphones or tablets and read through an app. The app gives clear, easy-to-understand descriptions of the trouble, unlimited vehicle-specific repair reports for fixes, a point-in-time snapshot of the moment the OBD2 sensors registered the issue and the ability to run a simulated smog test to head off surprises at inspection. Owners of smaller-screen smartphones won’t find the app as readable or useful as those with bigger screens. Some owners say it can lose the connection to the phone or tablet and the manufacturer recommends not leaving the sensor plugged into the port.
The Foxwell NT301 is a traditional handheld scanner that plugs into the OBD2 port with a cord. Trouble code data is displayed on a 2.8-inch color screen augmented by color-coded fault lights. It also functions as a battery tester and comes with cables with alligator clamps for that purpose. Owners like its rugged construction and large control buttons, but aren’t happy with the 3-foot OBD cable’s short length.
The Autel MaxiCom MK808 is an excellent OBD2 scanner meant for the advanced DIY-er with professional-level functioning. It performs 25 different service functions, works on 56 brands of cars and the rugged handheld tablet-style scan tool can give its information in 13 languages.
Getting an OBD2 scanner for well under $100 involves some compromises. Still, the Ancel BD310 is a useful basic scanner with a trick or two up its sleeve. Used as a handheld plug-in scanner, it will read and clear check engine codes. But the BD310 also has Bluetooth functionality, connecting with your smartphone or tablet via an app that greatly broadens the range of data and solutions available. Downsides reported by users include spotty Bluetooth connection, app glitches and less-than-clear instructions.
Deciphering fault codes and enabling diagnostic functions in the newest vehicles with Advanced Driver Assistance Systems (ADAS) requires a scanner that packs a punch. The Autel MaxiCom MK906 Pro-TS is that scanner. It can scan the VIN for rapid vehicle identification. It performs 31 different service functions, including five “Hot Repair” functions: oil life reset, Tire Pressure Monitoring Systems (TPMS) reset, Electronic Parking Brake Reset and Anti-Lock Braking System (ABS).
Additionally, the MS906 Pro-TS can access all electrical systems like the supplemental restraint system (SRS), engine, transmission, chassis, steering, airbags, air conditioning, air suspension, cruise control and more. It has two cameras: 16 megapixels at the rear and 5 MP up front.
OBD2 readers, short for Onboard Diagnostic II, are like a CSI investigation tool used for tracing and correcting faults deep in the subsystems of your vehicle. The standard OBD2 language applies to nearly every internal combustion passenger vehicle made after 1996, though readers vary in how deeply into your vehicle’s subsystems they can probe. Inexpensive units will read the basic codes for common ailments like oxygen sensor and throttle position sensor failures, while premier models allow users access to ABS and airbag systems, as well as make actual adjustments to a vehicle’s operating parameters. Users looking for confirmation of a suspected faulty part or as a foil against being overcharged at the shop will find a mid-priced reader a valuable addition to their tool kit that will pay for itself in no time.
We evaluate all OBD2 readers based on these weighted metrics:
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There are three primary types. Code readers are the least expensive. They’ll tell you if something’s wrong and that’s pretty much it. A step up from that is a full-featured scanner. With those, you get more information about more systems in the vehicle. Finally, there are professional OBD2 scanners, with still more functions (such as the ability to change vehicle settings), more diagnostic power with updated info from automakers, touchscreens and more features.
The most basic ones can do two things—find out what caused a “check engine” light to come on, and turn it off. More upscale models can also check on dozens of vehicle functions, and perform extensive diagnostic tests and services, including anti-lock brake bleeding, vehicle key fob programing and ADAS diagnosis.
While owning your own OBD2 scanner can save costly trips to the dealership or mechanic, there are places (most major auto parts stores) that will do OBD2 scans for free, or even let you take a scanner out into the parking lot to do it yourself. A realistic assessment of just how often you’ll use any tool is always helpful. No matter the path you choose, educating yourself about what may be wrong with your vehicle can potentially save you hundreds of dollars on potentially unnecessary repairs.
They are supposed to work on every car and light truck made after 1996 when the OBD2 standard was adopted, though there are a small number of exceptions. A few vehicles built before 1996 also have OBD systems (OBD1). Some scanners may not have vehicle-specific diagnostic ability. Check with the manufacturer and/or online model forums about specific vehicles before investing in a scanner for an older vehicle.
While scanners themselves are very accurate, deciphering the codes is where issues can arise, as many auto manufacturers, particularly European brands, have model-specific codes. Higher cost scanners may have the ability to read model-specific codes, and perform specific diagnostic testing and service functions. Different scanners will provide either simple alphanumeric codes that need to be looked up while others give a direct diagnosis. For example, some will tell you the code “P110” with the more helpful “Oxygen Sensor” description.
Bluetooth OBD2 scanners add functionality and flexibility, allowing for readings and inputs via smartphone, tablet or laptop. But, as with any wireless application, Bluetooth is imperfect. Connections can drop or be difficult to establish. Bluetooth devices are range-sensitive. What works in one instance may not work the next time, regardless of your distance from the scanner. The more professional grade scanners are equipped with the latest wireless Bluetooth vehicle communication interfaces and latest communications protocols, so the heftier units are more reliable.
Scanners do draw a small amount of power, so leaving one plugged into the port of a car that’s not running could, over time, drain its battery. There are several units for sale that monitor OBD status, and also provide GPS readouts of your location and vehicle speed. These are generally small, dashtop mounted accessories. Some scanners are not intended to be left in the OBB2 port, and can potentially trigger additional warning lights.
According to EPA regulations, these “green” vehicles are required to have onboard monitoring capabilities that may vary from monitoring through an OBD2 port. Visit www.epa.gov and search for “On-Board Diagnostic (OBD) Regulations and Requirements: Questions and Answers” to read through the agency’s document on the scanners.
A car-crazy California kid, I’ve been writing and talking about vehicles for 25 years on TV and radio, in print and online, including AAA magazines in Arizona, Oklahoma, Northwest Ohio, South Dakota and the Mountain West, as well as BBC Autos. I serve as vice president of the Western Automotive Journalists, a professional group for automotive writers based in San Francisco, and have no relation to McKeel Hagerty of Hagerty Classic Insurance, who is younger, better looking and wealthier.
Code Reader For Cars Harbor Freight Brian Armstead has been involved in print, radio and television for over 46 years. He is president emeritus of the Washington Automotive Press Association, a North American Car, Truck and Utility of the Year (NACTOY) juror and is a regular contributor to several automotive media broadcasts and websites. In his spare time, Brian enjoys tending to the care and feeding of his Volvo, Mercedes-Benz and Land Rover vehicles.