How one Bluetooth adapter can change the way you use your car

You'll finally be able to pinpoint what the check engine light means.

person standing in front of car while writing on a clipboard
The on-board diagnostics (OBD) port isn't just for your mechanic.Deposit Photos

If your car is less than 24 years old, it has a small white diagnostics port that mechanics use to analyze problems and gather data about your vehicle. But by simply pairing your smartphone with a cheap Bluetooth adapter, you can harness that power for yourself and turn your regular car into a smart car.

The plug, known as an on-board diagnostics (OBD) port, lets external devices talk to and gather data about your car. You can use it for mundane stuff like diagnosing check engine lights or gauging your fuel efficiency, but you can also do fun, fancy stuff, like tracking your car with GPS or automatically turning on the smart lights inside your house when you park at home.

What OBD is and how it works

Every car manufactured since Jan. 1, 1996, must have an OBD-II port—a more advanced version of the original—installed somewhere on the vehicle and accessible from the driver’s seat. It could be under the dashboard, near the ashtray, or by the steering wheel.

The mandate evolved out of the U.S. Environmental Protection Agency’s emission standards, which require vehicle manufacturers to measure and regulate emissions and the long-term maintenance of their vehicles. By the mid-1990s, built-in computers were used to monitor emissions data, so the EPA said they had to be accessible. If you live in a state where regular emissions tests are required, you may have seen an attendant plug into this port to make sure your car isn’t spewing too much toxic gas.

Choose your adapter

To use your OBD port, you’ll need a Bluetooth adapter that will connect with your phone and an app to interpret the data that comes in. Basic adapters are cheap—often under $30—but more expensive ones come with many useful extra features. Like the phones they pair with, there are countless options available, but here are a few to get you started:

The bare-bones option: This adapter from BAFX uses a simple Bluetooth connection and doesn't come with an app of its own. You can, however, pair it with an app like Dash to analyze check engine codes or gauge your fuel efficiency. This and some other cheaper adapters rely solely on your car's battery, which can drain some vehicles if you leave the adapter plugged in and don't drive the car enough. These are ideal if you want to keep an adapter in your glove compartment, but don't need it all the time.

The always-connected option: This adapter from OBLink provides a more complete OBD experience without breaking the bank. It automatically shuts off when not in use, so you won't risk draining your car's battery. The company also makes its own basic app to access data, including fuel efficiency and diagnostic codes. It doesn't come with fancier features like GPS tracking or a cell connection, but it provides a little more peace of mind than cheaper adapters if you want to leave it in all the time.

The total package: For all the coolest bells and whistles, Automatic's latest adapter has GPS and connects wirelessly to an LTE network so it can update your phone even when it's out of Bluetooth range—helpful if your car gets stolen or if you're letting someone else drive. You can also pair it with services like IFTTT to make it perform all kinds of tricks. That means you'll be able to tell your smart lights to automatically turn on when you get home or log your work-related trips to a Google spreadsheet so you can expense them later. Automatic is the most expensive option of the bunch, but it offers far more than basic adapters can.

For the most part, OBD adapters work with any car, but some hybrids or electric vehicles may not support certain adapters. Be sure to check and make sure your car is compatible before you buy.

What you can do

Depending on the adapter you get, there’s a range of fun things you can do with it. We’ll go over a few and describe the type of adapter you’ll need for each one.

1. Find out what's wrong with your car: When your check engine light comes on, the reason could be one of literally thousands of potential problems. To find out which it is, plug in your OBD adapter and use an app like Dash to find out exactly what's wrong. In Dash, make sure your OBD adapter is connected—you may need to tap the blue Connect button in the center of the bottom navigation bar—then tap the car icon in the bottom left corner of the screen to see the cars you've registered with the app. Select the car in question (if you have more than one), and tap Engine Alerts to see information on what went wrong, what parts are needed to fix it, and how much a repair usually costs. It also links to RepairPal to help you find someone who can assist.

2. Locate your car with GPS: Some adapters have built-in GPS that can log your car's location and send it to your phone. This alone can be useful; if you can't remember where you parked, for example. However, when paired with cell service, like in Automatic's adapter, it can relay your car's location even when the vehicle is away from home. If your car is stolen or you're letting your teenager borrow it, you'll be able to see exactly where it is at all times.

3. Improve your driving habits: Did you know you can get better gas mileage if you drive a little differently? Many of us slam the gas pedal down at the first sign of open road, only to brake when we near another car, then accelerate hard all over again. Apps like Dash can tell you how you're driving and even grade your performance behind the wheel after each trip. This can be handy for teaching new drivers good habits early on. At the end of each trip, you'll be able to see a precise dollar figure for how much the trip cost you, so if you want to save some money or need to log the expense for work, you'll have the information you need.

4. Connect to your smart home: Automatic is one of the few OBD adapters that works directly with simple programming services like IFTTT, which makes it an ideal candidate to handle your smart lights. You can use formulas like this one to automatically turn on your Philips Hue (or other) smart lights when you're parked at home. If you have a smart garage door opener, you can program it to automatically close as soon as you turn your car off, too