Diagnosing modern vehicle issues means somehow talking to the onboard computer systems. These systems are capable of performing in-depth vehicle diagnostics on the fly and storing the results for retrieval later. Sometimes the results of those diagnostics mean the check engine light will turn on, while other times an issue may just get logged for future reference. Regardless of how the information is acquired, you will need a special tool to read the OBD codes. That’s when having an OBD2 scanner on hand makes sense. Here’s how to use OBD2 scanner tools on your own car.
Back in the early days of onboard diagnostics, it wasn’t exactly easy to interface with the computer. In some cases, you had to insert a jumper wire across the access port, turn the ignition key in a special pattern and then count the number of times the “check engine light” flashed. Not exactly easy. True OBD scanners were the realm of dealership service departments. But things changed in the early 1990s when OBD2 became the national standard.
Most OBD scanners you will come across now are actually code readers. They are designed to access the diagnostic code information stored by the onboard computer and display it to the user. It is a one-way street for the most part with the exception of having the ability to erase any stored diagnostic codes.
Some OBD scanners are also diagnostic tools that can not only read stored diagnostics codes, but also communicate back to the onboard computer systems. For example, this Bosch OBD2 scanner is able to manually control components in order to test them. For example, it can open and close a drive-by-wire throttle body while the technician observes to make sure it is moving correctly. This is extremely handy when diagnosing an issue to help isolate components for testing. Unfortunately, a bidirectional OBD2 scanner requires deep understanding of how a certain vehicle’s computer operates. OBD scanners with two-way communication capability are often much more expensive than a simple code reader.
How to Use an OBD2 Scanner: 7-Step Tutorial
Using an OBD2 scanner is fairly straightforward. We recommend taking a few minutes to read over the instruction manual for your particular OBD2 scanner so you are familiar with the buttons and screen.
- Locate the OBD port. Federal law requires that the OBD port is located within two feet of the steering wheel. It is possibly located out in the open or behind a plug/cap/door.
- Plug the OBD2 scanner into the OBD port.
- Turn on the vehicle. For key start ignition vehicles, turn the ignition switch to the “on” position; it is not necessary to start the car. This puts the vehicle in “accessory” mode. For push button start vehicles, refer to your owner’s manual for how to put the vehicle in “accessory” mode.
- Once the vehicle is in “accessory” mode, the OBD2 scanner should begin communicating with the vehicle.
- Following the instructions included with your particular OBD2 scanner, begin a code scan. This should only take a few minutes.
- The OBD2 scanner will indicate if there are any stored codes found. Write down any fault codes so you can look them up later.
- Once the OBD2 scanner has scanned the onboard computer, you may turn off the vehicle and unplug the scanner.
Now that you know the fault codes, you can now begin to diagnose the problem. Luckily, OBD2 codes are mostly standardized across the industry, so a code P0030 for an oxygen sensor is the same whether you drive a Scion xB or a Nissan Titan.
Decrypting the Code
The two most common kinds of OBD fault code types you will find are pending and confirmed. A pending code means the onboard diagnostic system recorded an issue somewhere during its self-check procedure. If the issue does not occur again, the pending code will get erased from computer memory. A pending code will not cause the check engine light to illuminate. On the other hand, if an issue occurs again, it is then confirmed and stored as a fault code. A confirmed fault code will turn on the check engine light, alerting the driver that there is an issue.
With Great Power Comes Great Responsibility
Your OBD2 scanner will likely have the option to erase any stored trouble codes that are found. Use this option with caution. Wiping stored OBD codes also resets the emissions monitoring system. If you live in an area that requires an annual emissions test, the emissions monitoring system must be ready in order to pass. For the emissions system to be ready, it must have the ability to complete several different self-tests from catalytic converter function to fuel tank vapor recovery. Some of these tests are easy to complete, while others require certain conditions like a full fuel tank or a cold start. Wiping OBD2 codes is not a cure-all for a check engine light and could derail your next emissions test if you are on a tight deadline. The best course of action is to fix the problem that caused the error code and drive the vehicle normally. If the OBD2 system does not detect the issue again after a certain number of starts, the check engine light will go out on its own.
Now that you know how to use an OBD2 scanner, you are ready to tackle that check engine light. Simply head to your local NAPA Auto Parts store or on NAPAonline and pick up your own OBD2 car scanner. When you shop at participating NAPA Auto Parts stores and on NAPAonline, make sure to take advantage of NAPA Rewards. For every $1 you spend, you earn 1 Point. When you earn 100 Points, you get an automatic $5 off your next purchase. You can buy your new OBD2 scanner tool several different ways. Don’t feel like leaving the house or don’t have time? NAPAonline offers One-Day Shipping on more than 160,000 products.
If using an OBD2 diagnostic scanner still seems impossible, your local NAPA Auto Care is ready to help. Their ASE-certified and trained technicians have all the best OBD2 scanner options at their fingertips along with the knowledge to use them. Once your vehicle is scanned, they can then help you decide the best course of action for repairs.
With an automotive writing career spanning over two decades, Brian has a passion for sharing the automotive lifestyle. An avid DIYer he can usually be found working on one of his many project cars. His current collection includes a 1969 Olds Delta 88 convertible, BMW E46 sedan, and a slant-6 powered 1975 Plymouth Duster.