What Is the OBD-II Port and What Is It Used For?
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If you purchased a car after 1996, chances are it has an OBD-II (On-board diagnostics II) port. Every car or truck on the road manufactured after 1996 is legally mandated to have one installed.

OBD-II is an on-board computer that monitors emissions, mileage, speed, and other data about your car. It’s connected to the Check Engine light, which illuminates when the computer detects a problem.

The OBD-II on-board computer features a 16-pin port located under the driver’s side dash. It allows a mechanic or anyone else to read the error code using a special scan tool.

OBD-I vs. OBD-II

example of an obd-ii port
Image Credit: Alain Van den Hende/Wikimedia Commons

Before OBD-I, each manufacturer had their own set of standards for OBD, meaning that mechanics had to buy expensive scan tools for each manufacturer. OBD-I was first introduced in 1987, and started the standardization of onboard diagnostics.

It had sensors that detected emissions and was able to minimize them through emissions-controlling valves. However, it had many problems and shortfalls.

As a result, in 1996 car manufacturers started to equip cars and trucks with an OBD-II port. Every system is mostly the same, but there are slight variations. These are known as protocols, and are specific to vehicle manufacturers.

There are five basic signal protocols:

  • SAE J1850 PWM: Pulse Width Modulation, used in Ford vehicles
  • SAE J1850 VPW: Variable Pulse Width used in General Motors vehicles
  • ISO9141-2: Used in all Chrysler and a variety of European or Asian vehicles
  • ISO14230-4 (KWP2000): Keyword Protocol, used in a variety of European and Asian imports as well as Honda, Jeep, Land Rover, Subaru, Mazda, Nissan, and more
  • ISO 15765 CAN: Controller Area Network, used on all vehicles manufactured after 2008

Pins 4 and 5 in all protocols are used for ground connections, and pin 16 is used for power from the car’s battery.

Once the computer senses a problem with the engine or any other component of the car it’s monitoring, it’ll trigger the Check Engine light. Some vehicles also blink the engine light if the problem is a very serious one.

How Does OBD-II Work?

Diagnostic Trouble Codes (DTC) are stored in the computer system. Codes can vary from one manufacturer to another. However, anyone with an OBD-II scan tool can connect to the port and read the diagnostic trouble codes from the computer.

The reason any OBD-II scan tool can read the codes is because of the standardized pinout. Scan tools can read from any of the protocols listed above. The standardized pinout is as follows.

  • Pin 1: Used by manufacturer
  • Pin 2: Used by SAE J1850 PWM and VPW
  • Pin 3: Used by manufacturer
  • Pin 4: Ground
  • Pin 5: Ground
  • Pin 6: Used by ISO 15765-4 CAN
  • Pin 7: The K-Line of ISO 9141-2 and ISO 14230-4
  • Pin 10: Used only by SAE J1850 PWM
  • Pin 14: Used by ISO 15765-4 CAN
  • Pin 15: The K-Line of ISO 9141-2 and ISO 14230-4
  • Pin 16: Power from the car battery

OBD-II scanners can connect to these ports and identify the trouble code from any manufacturer that uses one of the OBD-II protocols.

What Can Be Hooked Up to the OBD-II Port?

Traditionally, a mechanic would hook up a scan tool to the port to read the DTC. Less expensive scanners would only provide a numeric code, which the mechanic would then look up from the manufacturer’s manual or service website. More expensive scanners provide will provide text error codes.

However, in recent years, there are more advanced tools available for regular drivers who don’t want to have to depend on a mechanic to find out what’s wrong with their car.

One example is the OBDLink SX USB Adapter by ScanTool that lets you read the trouble codes with your laptop.

ScanTool OBDLink SX USB: Professional Grade OBD-II Automotive Scan Tool for Windows – DIY Car and Truck Data and Diagnostics ScanTool OBDLink SX USB: Professional Grade OBD-II Automotive Scan Tool for Windows – DIY Car and Truck Data and Diagnostics Buy Now On Amazon $29.99

This device lets you plug directly into the OBD-II port, and plug the other end into the USB port of your Windows laptop.

This transforms your computer into an advanced OBD scanner tool, plus you can even clear the Check Engine light with the OBDwiz diagnostics software.

If you prefer a wireless solution, ScanTool also offers OBDLink MX Bluetooth.

OBDLink OBD2 Scanner MX Bluetooth: Professional Grade OBD-II Automotive Scan Tool for Windows and Android – DIY Car and Truck Data and Diagnostics OBDLink OBD2 Scanner MX Bluetooth: Professional Grade OBD-II Automotive Scan Tool for Windows and Android – DIY Car and Truck Data and Diagnostics Buy Now On Amazon $64.95

This device lets you read your car diagnostics with your Windows blue-tooth enabled laptop, or your Android device.

It comes with free Windows and Android software to diagnose your car remotely.

Other Mobile OBD-II Scanner Apps

The computer system in your car is constantly monitoring various systems and components throughout your car.

This means that any device that plugs into the port can read the same information and pass it along to your mobile device. Imagine opening an app on your phone and viewing your vehicle’s current fuel consumption, temperatures, oil pressures, and more.

It’s possible today with any of the devices and apps listed below.

BAFX Products – WiFi OBD Reader (iOS)

wifi obdii

BAFX Products - OBD Reader for Check Engine Lights & Other Diagnostics (for iOS Devices) BAFX Products - OBD Reader for Check Engine Lights & Other Diagnostics (for iOS Devices) Buy Now On Amazon $26.25

This wireless OBD reader by BAFX Products transforms your iOS device into an impressive, advanced OBD tool. Not only can you read all diagnostics data from your car, but you can also monitor real-time data like:

  • Engine temperature
  • Fuel rate
  • O2 sensor voltages
  • Battery voltage level
  • Time your engine has been running

It’s a useful tool to monitor data about your car systems that your own dashboard doesn’t show you.

Keep in mind however that the third party apps that work with this device aren’t free.

Panlong Bluetooth OBD-II Car Diagnostics Scanner (Android)

panlong obdii diagnostic scanner

Panlong Bluetooth OBD2 OBDII Car Diagnostic Scanner Code Reader Check Engine Light for Android - Compatible with Torque Pro Panlong Bluetooth OBD2 OBDII Car Diagnostic Scanner Code Reader Check Engine Light for Android - Compatible with Torque Pro Buy Now On Amazon $10.98

If you’re looking for an inexpensive solution, you can’t go wrong with this OBD-II diagnostic scanner for Android by Panlong.

This device works with a variety of Android apps like Torque Pro, Torque Lite, or OBD Car Doctor. Just enable Bluetooth and you can view various sensor data, and diagnose error codes when your Check Engine light turns on.

Unlike most other devices in this price range, this device also lets you clear the error codes for minor things like a loose fuel cap.

iSaddle Super Mini Bluetooth OBD2 Scan Tool

isaddle obd2 scan tool
iSaddle Super Mini Bluetooth OBD2 OBDII Scan Tool Check Engine Light & CAN-BUS Auto Diagnostic Tool for Windows & Android Torque (Black Color, Super Mini) iSaddle Super Mini Bluetooth OBD2 OBDII Scan Tool Check Engine Light & CAN-BUS Auto Diagnostic Tool for Windows & Android Torque (Black Color, Super Mini) Buy Now On Amazon $11.99

Another inexpensive solution for your Android device is the iSaddle Super Mini Bluetooth OBD2 Scan Tool.

Just enable Bluetooth on your phone and connect to this scan tool to read information from your OBD-II port. The device can read all OBD-II protocols. You can use it with Torque Android software, or even ScanMaster software for your Bluetooth-enabled laptop.

And if it matters to you, you have a choice of three port adapter colors to choose from!

BlueDriver – Bluetooth Professional OBDII Scan Toolbluedriver obdii scan tool

BlueDriver Bluetooth Pro OBDII Scan Tool for iPhone & Android BlueDriver Bluetooth Pro OBDII Scan Tool for iPhone & Android Buy Now On Amazon $99.95

The BlueDriver Bluetooth Professional OBDII Scan Tool is for anyone who would like a more functional OBD-II port scanner. This scan tool is Bluetooth-enabled, and works with both Android and iOS devices.

It’s somewhat more expensive than other wireless port-readers on the market. However, it comes the sort of features you’d expect from the same expensive scan tools that mechanics use.

The device lets you use your mobile app to read and clear both basic and advanced error codes. It also includes advance tests like misfire counts, live data as digital readouts and graphs, and even repair reports from a frequently updated online database.

Automatic PRO AUT-350

automatic realtime car tracking
Automatic PRO AUT-350 Connected Car OBD II Adapter, Realtime Car Tracking via 3G and No Monthly Fee, Trip Tracking, Engine Light Diagnostics, Severe Crash Detection and Alexa Skill. Automatic PRO AUT-350 Connected Car OBD II Adapter, Realtime Car Tracking via 3G and No Monthly Fee, Trip Tracking, Engine Light Diagnostics, Severe Crash Detection and Alexa Skill. Buy Now On Amazon $155.22

Reading and clearing error codes is useful, but if you really want to have access to real-time data, then the Automatic PRO AUT-350 OBDII adapter is the way to go.

It’s one of the more expensive options, but the features are simply amazing.

  • 3G connectivity provides remote vehicle information no matter where you are.
  • Get real-time vehicle data even when you’re far from your vehicle.
  • Detects crashes and sends emergency services to help you.
  • Integrates with the Echo, Nest, and IFTTT.
  • GPS tracking enabled so you always know the location of your car.

While the price sets this advanced scan tool within the range of many expensive tools mechanics use 5 Ways to Save Money on Car Repairs and Avoid Mechanic Rip-Offs 5 Ways to Save Money on Car Repairs and Avoid Mechanic Rip-Offs The smallest repair on your car can cost a whole lot of cash. These five car information tools can help you understand and car better and save money in the process. Read More , all of these impressive features make it well worth the cost.

Taking Advantage of Your OBD-II Port

The OBD-II port has been available in vehicles for many years, but only recently has been accessible to regular drivers. Having these devices and apps gives you much better insight into what’s going on with your vehicle, long before any major problems ever occur.

Many of these port scanners come with location tracking features. If that’s what you’re more interested in, then make sure to check out some of the best GPS trackers for your car What's the Best GPS Tracker for Your Car? What's the Best GPS Tracker for Your Car? A GPS tracker for your car lets you keep track of it anywhere. Here are the best car GPS tracker units for a variety of uses. Read More . Even though they don’t show you your car diagnostics, at least they’ll make sure you never get lost.

Explore more about: Automotive Technology, Bluetooth, OBD-II.

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  1. Josh Veach
    June 4, 2016 at 11:17 pm

    Is there an obd 2 tool software that I can load on windows 10 and use my ObdSX or MX Bluetooth tool with that allow me to turn features on and off like shutting off air bag, turning GM's AFM off "8cyl to 4cyl mode" or boost the idle rev limit because I have about 20 2001 to 2015 GM, Fords, and a few MOPAR that sit and idle on the job site for hours and hours and its hard on them and easier if you up the rev limiter I heard.

    • Thomas Deininger
      December 31, 2018 at 4:00 am

      What kind of job do you have that requires 20 idling vehicles?

  2. Teri
    May 26, 2016 at 6:55 pm

    can I plug in my battery maintainer through the OBDII port? It comes with a 12V plug adapter but the power cuts off to that when I turn off the vehicle.

    Also, could I plug in a portable power bank into the OBDII and use it as a memory saver for when my battery gets disconnected? I heard it could be used for that but I'm worried too much power going into the port could hurt something.

  3. esraa elkholy
    December 11, 2015 at 12:28 pm

    i just want to know if i used Can bus shield with obd2 port cable for my KIA Car , what will be the sample output from the port of the can bus ?
    Is it 1's and 0's or i should display it on a certain software to get the output sample readable for me ?
    is it accessible to show me the output from the can bus if i connected it to a machine link or a raspberry pi?
    what will be the output , is it voltages or signal bits, is it a hexadecimal indication ?
    thanks in advance

  4. John
    December 1, 2015 at 4:47 am

    Can this tell you things like, why the interior lights are not working? And if any relays or fuses are gone in a car?

  5. Scott M.
    January 3, 2015 at 2:59 am

    The following are good places to get more information on different products. Shopping at retailers like Amazon might not give you details and info about available options. I've purchased a ScanGauge II for my brother and OBD-II reader from ScanTool that I use with an old 7" Asus eeePC. PLX Devices also make OBD-II readers for Android and iOS as well as a stand-alone unit. The PLX Kiwi and the ScanGauge II are small stand-alone units that can be mounted in the vehicle for those that don't have an Android or iOS device, or want to monitor engine sensors (temperature, voltage, etc) or fuel economy.
    http://www.plxdevices.com/product_cat.php?id=SCAN
    http://www.scantool.net/
    http://www.scangauge.com/

  6. horribilis
    December 31, 2014 at 8:11 pm

    I've always wondered how those work! I couldn't have asked for a more cogent explanation. Thanks for helping me educate myself.

    • Taylor
      January 4, 2015 at 7:49 pm

      You're absolutely welcome. Thank you for reading and commenting. :)

  7. Doc
    December 31, 2014 at 12:16 am

    "...focus on what lead to OBD-II." I think you meant "led," not "lead." :)

    • Taylor
      January 4, 2015 at 7:53 pm

      You are absolutely right. Sorry about that.

    • Taylor
      January 4, 2015 at 7:52 pm

      Wow! A shame it doesn't seem like it's iOS compatible though. It doesn't seem like many bluetooth scanners are.

  8. jshal
    December 30, 2014 at 2:58 pm

    Did you mean "braking...?"

    • Taylor
      January 4, 2015 at 7:52 pm

      Yes I did, sorry about that. :)