Left Arrow Swipe for more categories Right Arrow

Understanding OBD and Using an OBD Reader

on May 1, 2019

Understanding OBD and Using an OBD Reader

on May 1, 2019

You’re driving in your car. The pressures and duties of your day are circling in your head. That’s when your check engine light pops on in front of you. What does that mean? It could be just about anything. Diagnosing problems with your vehicle by using an OBD Reader is a great way to alleviate anxiety and avoid being taken advantage of by a greedy mechanic.

That’s why it’s important to know about On-Board Diagnostics (OBD). Familiarizing yourself with the OBD system in your vehicle will save you money, stress, time, and will help you pinpoint small problems before they become bigger ones.

What Is OBD? On Board Diagnostics

OBD by definition is a computer-based system installed in vehicles and was introduced in the 1980s.  The initial purpose was to monitor and control mobile emissions as per the Environmental Protection Agency. In the 1970s, when the United States Congress passed the Clean Air Act, car manufacturers began making cars and trucks with an electronic fuel injection system. This meant that sensors would be put in the engines of these vehicles to monitor engine performance and minimize pollution. These sensors could also be used to diagnose problems within the engine and fuel delivery system.

By 1996 in OBD history, vehicles in America were aligned with standards and practices set forth by the Society of Automotive Engineers (SAE) and with a connector plug and a list of diagnostic test codes. As vehicles and their technology have advanced throughout the years, OBD2 readers have been modified, and the code list has been expanded to include more information and diagnose a vehicle’s performance more efficiently.

What Is OBD-II?

OBD-II (OBD2) was the title given to the more sophisticated on-board diagnostic systems installed in vehicles in the mid-1990s. Vehicles manufactured before 1994 had the original OBD system that was retroactively labeled OBD-I. There was a transitional period from 1994 to 1996 when some cars were still being assembled with OBD-I, but by January 1, 1996, OBD-II became the universal standard.

Check Engine Light

When a “Check Engine Light” comes on in your vehicle, it can mean several things.  Generally, it indicates that a sensor in the engine, exhaust, or transmission has sent unusual data to the computer. Any time one of the car dashboard lights clicks on, the OBD-II system is your best bet to weed out the problem rather than needlessly replacing parts through trial and error.

The “Check Engine Light” may flash momentarily and stop. This is indicative of a malfunction that lasted very briefly but is not serious. If the “Check Engine Light” stays on, it means the problem is more serious. If a dashboard light is continuously flashing, it means the problem is severe, and the vehicle needs to be shut off immediately. Any time these things occur, a “freeze frame” of any sensor readings is recorded in the vehicle’s central computer. This is a great thing to know because an OBD-II scanner can access this information even after the “Check Engine Light” has gone off.

OBD Reader

The device used to read the signals output by the OBD system goes by a few common names:

  • OBD Port Reader
  • A Diagnostic Code Reader
  • OBD Scanner
  • Auto Code Reader

These terms all refer to the same piece of equipment. An OBD-II scanner or reader is the tool that connects to the OBD port in your vehicle to access the computer system and diagnose the trouble your car is having.


The diagnostic readings used by mechanics are read through the OBD connector. Repair shops and dealerships will usually charge a fee to do a diagnostic test on a vehicle. This used to be due to the expensive equipment required to access the information for the OBD system. Over time, more inexpensive and simple scanning tools have been produced. The advent of cheaper, smaller OBD2 scanners makes it more practical for anyone to access the OBD signals in their vehicles and handle repairs more efficiently.

OBD Port Location

Vehicles equipped with OBD-II will have the port (or connector) under the dashboard on the left side of the steering column. However, if your vehicle is older and equipped with an OBD-I system, the port could be located in the engine compartment or the fuse box. The port will be shaped in a trapezoidal or rectangular format.

What’s the Best OBD2 Scanner?

The best OBD scanner for you is going to be the one that reads your particular vehicle’s OBD system most comprehensively. Check your vehicle owner’s manual to ensure you know whether your car is using an OBD-I or an OBD-II system. Although OBD-II codes are universal, manufacturers also have extra codes to pinpoint more problems.

You may want to contact the service department at your local dealership to get recommendations on scanners that will best read the codes specifically for your vehicle. From there you can shop online or at any store with an auto parts department and find an OBD2 scan tool that suits you in terms of expense and simplicity. You can even rent or borrow a car diagnostic scanner. Many parts stores will lend out an OBD-II code reader free of charge. But if you feel that you’ll be doing a lot of upkeep and preventative maintenance on your car, you’d be better off buying a more high-end device for long term use.

How to Use Diagnostic Code Reader

Make sure you shut off your vehicle completely before connecting the car diagnostic scanner. Be sure that you’re plugging the device in properly. It should slide in easily unless it’s upside down. Once the code reader is plugged in, turn the key in the ignition to the “ON” position. The scanner should power on. From this point, the next step will differ from one device to another. Some code readers will ask you to put in vehicle information such as the vehicle identification number (VIN). Others will simply begin scanning and give you the stored trouble codes.

Once the scanner gives you your diagnostic trouble codes, you can do a quick internet search to diagnose the repair. On newer model OBD2 code readers, both the trouble code and the code description will be displayed all in one shot. Some of these scanners will even tell you which parts are causing the problem so that you can repair or replace them.

OBD-II Codes

Vehicles are sophisticated machines comprised of thousands of parts and electronics. To pin-point each problem specifically, there are hundreds of OBD-II codes that your car’s computer system can relay to a diagnostic scanner.

To decipher what issue the on-board diagnostic system is warning you of, you may need to do some quick research. Once your OBD reader has delivered the codes, copy them down, and a simple internet search will fill you in. There are plenty of web sites that contain a search engine to type in the specific code, or you can find sites with a list of OBD codes.

OBD Reader App | On Board Diagnostics App

Technology is constantly improving, and OBD technology is no exception. With new wireless Bluetooth OBD-II tools, the device syncs up to a phone or tablet. This makes the scanning of your vehicle computer system faster and easier. There are plenty of free apps to download onto your mobile device that will store codes onto a phone or tablet’s memory. Bluetooth Scan tools themselves can be purchased at a surprisingly low price, and some models can even diagnose potential problems in your car that haven’t activated a code signal yet.

How to Clear OBD Codes

Once you’ve diagnosed and repaired the problem with your vehicle, you’re going to want to clear the OBD codes from your system. This will turn off the dashboard lights that were on before the repair. This is important in that it will ensure that the issue your vehicle is experiencing has been successfully dealt with.

If your check engine light remains lit once you have cleared the code, you may have missed the problem. If you are using an app on your phone, or a hand-held scanner device, find the option on your device to “Reset Diagnostic Trouble Codes (DTC).” 

Once you turn your car on again, your dashboard Check Engine Light should be off.

Everyone Can Use OBD-II

Nobody wants to handle a problem that has gotten out of hand. Diagnosing small problems before they become serious will save you from a lot of trouble.  An OBD2 scanner will help you spot problems by yourself. This way, even if you’re taking your car to be fixed by a professional, you know what to expect.

Utilizing an OBD scanner can also save you a significant amount of money.  Having the ability to detect issues in your car on your own allows you to avoid diagnostic fees.  While it’s likely that you will still have to pay a diagnostic fee after bringing in your vehicle for repair, you can avoid it if the discovered issue was something you can easily fix by yourself.

OBD Readers have become so much more user-friendly over the years that everyone should be able to benefit from the information they provide. Be sure you buy the right OBD hardware that is right for your vehicle and get a device that is easy to read and makes sense to you.

Or Call 888-980-7459
By submitting this form I am giving DriveSmart consent to contact me by email or telephone at the telephone number(s) provided above even if I am on a corporate, state or national Do Not Call Registry. Note that this may include the use of an automated dialing system. I understand that consent is not a condition of purchase. The DriveSmart privacy policy governs our data collection policy.
Please correct all errors before submitting.
By submitting this form I am giving DriveSmart consent to contact me by email or telephone at the telephone number(s) provided above even if I am on a corporate, state or national Do Not Call Registry. Note that this may include the use of an automated dialing system. I understand that consent is not a condition of purchase. The DriveSmart privacy policy governs our data collection policy.
Thank you! An agent will be contacting you shortly.
© 2024 DriveSmart. All rights reserved.
Drivesmart Auto Care Inc. BBB Business Review
Disclosure: DriveSmart offers Protection Plans or Vehicle Service Contracts (VSC) may be referred as “extended car warranty”, or “auto warranty”. A VSC is not a warranty but provides repair coverage for your vehicle after your manufacturer’s vehicle warranty has expired. The VSC contract is with you and the vehicles owner and the VSC provider or administrator that will state what is covered in each plan.