What Is an OBD2 Scanner and How Does It Work?


byJonathon Klein|
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There it is. On your dashboard. Staring at you, mocking you, making you plot insurance fraud: your car’s check engine light. That little bugger has been on your dash for weeks now and you haven’t been able to figure out why its light is lit. No, you don't need to burn the car to the ground, but it’s time to break out the technology. It’s time for an OBD2 scanner

While formerly the stuff of professionals at shops and dealerships, OBD2 scanners have become almost household items as cars have become more complex. Underneath your hood are sensors for nearly every vital and non-vital component, and an OBD2 scanner will help you make sense of most of the information they provide when they fail. 

But what does an OBD2 scanner do and how does it work? Never fear, intrepid DIY’er, I’m here to illuminate your way, just like that damn check engine light is illuminating your dash. Let’s fix that. 

Andrew Collins

What Is an OBD2 Scanner?

OBD stands for “on-board diagnostics” and if you own a car that’s from 1996 to today, beneath the driver’s side dash there’s a little plug/port that resembles the port you’d plug your desktop computer’s monitor into on the tower. This is your car’s OBD2 port and is designed to help automotive technicians to diagnose faults and other issues your car may have by recording codes that mean various things.  

An OBD2 scanner is a small electronic device that plugs into your car’s OBD2 port that reads those codes. As mentioned above, this was once the tool of professional mechanics and dealerships. However, as with all technology, it became cheaper and cheaper to manufacture and the public’s desire to work on their own vehicles made them become consumer tools.  

How Does an OBD2 Scanner Work?

Plugging an OBD2 scanner into the OBD2 port is a fairly simple affair. You just do what Glade taught you, “Plug it in, plug it in!”

Once the OBD2 scanner is plugged in, there are various versions of what comes next. Most OBD2 scanners are battery-powered, so you’ll have to turn them on in order to read the engine’s codes. Others, however, use the power from the OBD2 port itself to power the device. There are also Bluetooth OBD2 scanners which come as a small dongle (get your minds out of the gutter) and pair to your smartphone. 

There are also various steps to reading your car’s codes, as each OBD2 scanner is slightly different. You may have to select a code read prompt or may read it automatically. But once it does, you’ll have the specific engine code that relates to your car’s fault, and potentially more as some more expensive code readers will tell you what the code means. While more basic ones will have you do a little internet sleuthing. 

Andrew Collins

As an example, you may see “P0171” pop up on your OBD2 scanner, but nothing else if you have a basic device. In that case, you can hit up Google—which at this point is like The Hitchhiker’s Guide to the Galaxy but more evil—and search out the code which tells you that your engine is running lean. 

Fixing the issue, however, may not be as easy as using an OBD2 scanner and could require a little more diagnostics. 

An OBD2 scanner, however, can also clear codes once you’ve fixed the problem. It can also clear the code if you don’t want to see the check engine light anymore, but you run the risk of, well, blowing up your engine or causing other irreparable damage to your vehicle. 

What’s the Best OBD2 Scanner?

Honestly, that really comes down to your need for convenience. Do you want one that reads you the code, what it may entail, and maybe a bed-time story? Cause you can go ham on super expensive OBD2 scanners. You can also go bargain-basement, but those don’t always work. Likewise, if you don’t want a reader with a long cord, you can grab a Bluetooth reader that fits in your car’s glove compartment. 

As for a few I’d recommend, here’s my shortlist: