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A brief intro to OBD-II technology

Every car sold after 1996 has one, but what does that OBD-II port under your steering wheel do?

Antuan Goodwin Reviews Editor / Cars
Antuan Goodwin gained his automotive knowledge the old fashioned way, by turning wrenches in a driveway and picking up speeding tickets. From drivetrain tech and electrification to car audio installs and cabin tech, if it's on wheels, Antuan is knowledgeable.
Expertise Reviewing cars and car technology since 2008 focusing on electrification, driver assistance and infotainment Credentials
  • North American Car, Truck and SUV of the Year (NACTOY) Awards Juror
Antuan Goodwin
4 min read
Actron PocketScan

Actron PocketScan
The Actron PocketScan is a good entry-level OBD code reader for the driveway mechanic. Actron

The primary purpose of the OBD-II connection is for emissions testing, but one of the first and most widespread applications available to consumers is the scan tool or code reader. These devices are sometimes battery powered, but newer units may be powered by the electricity provided by the OBD connection itself. When a Check Engine light is illuminated, these handheld devices connect to the OBD-II port and simply record and display any trouble code that the vehicle is sending. Users can then use the code to see what's wrong with the car and, once the problem has been fixed, clear the code from the vehicle's memory, deactivating the Check Engine light until the next issue arises.

These devices often just display the raw code, so you'll need some sort of code reference to know the difference between a P0302 and a P0455 (for the curious, the first means that your engine's second cylinder is misfiring and the second simply means that you've probably left your gas cap off). The most-advanced units may actually store the trouble codes in the device's memory to be retrieved later via USB and cross-referenced against Internet databases of code values and known issues, such as OBD-codes.com.

Data loggers

CarChip Pro
Data loggers like the CarChip Pro take up very little space. Davis

Where scan tools are designed to be connected to the OBD port for quick code reads, data loggers are designed to be semi-permanently connected to the vehicle. These smaller and often screenless devices stay with the vehicle as it is driven about, silently logging all of the information that the vehicle's OBD-II port provides.

This could be a great way to keep track of what your car has done over, for example, the last week; but for parents with teens, a data logger could be a good way to keep tabs on their young drivers' motoring habits. If Little Johnny decides to break 100 mph on the highway, you'll know about it--although, obviously, after the fact. Fleet managers can use similar technology to keep tabs on the manner in which their fleet vehicles are being driven.

Fuel economy meters

Check out our full review of the PLX Kiwi for more details. CNET

With more attention being paid to maximizing fuel economy, more and more we've been seeing devices that take advantage of the data supplied by the OBD-II port to report vehicle fuel economy using an external display. The standard PID set doesn't explicitly include a fuel economy parameter, but there is often enough information about the engine and fuel systems to fairly accurately extrapolate. However, some pre-2008 vehicles, such as our CNET Chevrolet Aveo, may supply insufficient data to these fuel economy meters, resulting in ludicrously inaccurate readings. Caveat emptor.

In addition to reporting fuel economy, some of these devices will give drivers reports of their historic fuel economy. Others will display ECO lights or graphics to coach drivers toward more miles per gallon. Some devices, such as the PLX Kiwi, offer driving challenges to help train the user to be a more efficient driver.

Performance computers

Bullydog Triple Dog GT
The Bullydog GT is an OBD-II scanner with a focus on performance parameters and monitoring. Bullydog

With all of that info about vehicle and engine speed, steering angle, and the like flowing out of a standard connection, the OBD-II port can be of great use to enthusiasts looking to measure their vehicle's performance on a granular level. Just like aftermarket fuel economy meters can extrapolate miles per gallon, OBD-II-connected performance computers can estimate horsepower, torque, and 0-60 times or provide a virtual tachometer for vehicles that weren't equipped with an OEM tach.

Vehicle specific devices can even be set to parse the nonstandard PIDs to derive data such as boost pressure or engine load.

Future applications

Rev app for iPhone
The future of the OBD-II standard lies with apps like Rev, which combines vehicle data with GPS tracking to monitor performance on the iPhone. DevToaster

Like most data-driven technologies (such as GPS and cellular data), the future of OBD-II technology lies in convergence.

For example, newer OBD-II scanners and readers are starting to integrate Wi-Fi technology to wirelessly connect to a nearby laptop or smartphone for easier monitoring of a vehicle in a garage or on the road. For example, the OBDKey WLAN and the PLX WiFi allow a nearby iPod Touch or iPhone to stream OBD data for use in an app such as Rev or DashCommand.

GPS device manufacturers are starting to get in on the OBD-II game as well. Earlier this year, we saw the announcement of the Garmin EcoRoutes HD system, which pulls OBD data from a Bluetooth dongle to more accurately measure your fuel economy and driving habits to tell how greenly you're driving and how you can improve.

As aftermarket accessory manufacturers gain more experience with the OBD-II standard, we may begin to see even more innovative uses for this data. Maybe some enterprising GPS manufacturer will figure out how to use the OBD supplied vehicle speed and steering-angle information to increase tracking accuracy in urban canyons and tunnels. Whatever the next cool application of OBD tech will be, we think there's still plenty of mileage to be gotten out of this little port.