How Does OBDII Work

OBD System History

The On Board Diagnostic (OBD) is a term that refers to systems in the vehicle that self-report issues. The system has its origins in the 1960s. During that time the state of California began pushing for emissions standards (the State still continues pushing hard for this, by the way). The federal government passed the Clean Air Act in 1970.

This act set emission standards for car and the automotive diagnostic equipment was used to get the cars to consistently pass these standards. These OBD 1 tools were used to monitor the emission system. Eventually, car companies realized that they could keep track of and provide information for any number of systems in the vehicle.  The OBD 2 scanning tools give you a handle on what is going on in a modern car.

How Does OBDII Work?

The computer that is running or monitoring many of the systems of your car will check measurements at certain time intervals. Some of these might get checked multiple times per second, others may only be checked every few minutes, it depends on how your car manufacturer set their system.

Whenever a check is made the computer will compare the value displayed to the values that it is programmed to view as acceptable. This happens constantly as you are driving about and normally the values will match. Sometimes the computer will find a value that doesn’t fall in the acceptable range.


When this happens the computer makes a note of it. Often times, when that is recorded a warning light, will pop on somewhere on the dash. While normally it will be the check engine light, it could also trigger an oil light or some other light, depending on how your car is set up.

All that light tells you is something is wrong. If you took it to a mechanic, they would hook it up to a diagnostic tool that would tell them what the issue was and may even lead them through how to fix it. An OBD 2 scanning tool is merely a home version of that device.

OBD-II Diagnostic Connector Pinout

Bus Positive Line
Manufacturer Discretion
Chassis ground
Signal ground
Manufacturer Discretion

Manufacturer Discretion
Bus Negative Line
Manufacturer Discretion
Manufacturer Discretion
Manufacturer Discretion
Battery voltage


Standard Interfaces Types

When you start looking into the Best OBD2 Scan Tool you will find that there are two main types. The first is a lower cost option known as a code reader. This tool will plug into your car and read then display any codes that are causing lights, such as the check engine light, to the flag. This device will allow you to clear the code as well. Normally you will get a book with a list of things the codes could mean or you could search online. This isn’t bad for basic repairs and clearing out codes, but it can be somewhat vague in certain areas.

As you move higher in the price brackets you’ll also find some code reader options. While there is no hard and fast line to easily say one is a very functional code reader and one is a lower end scan tool, overall the scan tools will do more. Frequently, in addition to the code, the is causing the flag a scan tool will give you some definitions to save you digging through a book or searching online. These tools may also have options to pass the codes and definitions via Wi-Fi or Bluetooth, some can even connect directly to a printer. Overall these types of devices will come with a lot more features.


When you start looking at these devices, one way of coming up with the best OBD2 scan tool is to compare the features. In general, more features will cost you more money up front, but if it saves you a trip or two to your mechanics shop they could save you a bunch of money in the long run.

The first feature to look at is a memory option. Some models will allow you to store a list of codes that have come up tagged with your vehicle’s VIN so that you can see if there is a pattern of issues that is arising. This can help you to remember what problems you’ve encountered and how often they have popped up, just in case you miss place your notes about how long it has been since you have done any given maintenance task. Some devices may even have a USB option to download this memory onto your computer for long term storage.

Another great feature that you will want to consider is having some sort of live data connection. The port that you need to plug these tools into tends to not be in the most conveniently placed areas. When you add in the cords tend to be rather short, you’ll see how useful live data streams can be. This will usually be done via Wi-Fi or Bluetooth. Either way, some devices will transmit your problem codes and other information to another device, making it much more comfortable to go through issues and even look up how to remedy situations. These connections also make it simpler to update your tool.

Lastly, you may want to consider the ability to print out your tool’s read out. You can use this to note down ideas as you research and even store it with a write up of what you fixed in order to make a hard copy of the maintenance done on your vehicle

Best OBD 2 Scan Tool Brands

1.Autel Scanner


Autel makes professional diagnostic tools for the automotive industry. But what’s more, they also make accessories and equipment for the automotive aftermarket. If you have to spend any serious amount of time in this hobby you have probably at least heard of them. They continue to strive to bring out new tools and equipment, investing at least 20% of their annual revenue into developing new products.

Check out all Autel products available on OBD2TOOL.

2.Launch X431


Launch is based in California and they are striving to produce automotive diagnostic tools that are both highly innovative but still cost effective. They pride themselves on offering tools and software that can cover just about every car sold in the United States today. As such, they employ quite the team of engineers and some of the leading experts in the field.

Check out all Launch products available on OBD2TOOL.



OBDSTAR persists on innovation with self-owned intellectual property, professional marketing, and factory. Taking mission of high-quality products, technology and service for Auto field. Besides, OBDSTAR employs large quantity of rich experienced engineers who are especially concentrated on developing automotive electronic equipments. In addition, OBDSTAR has excellent after-service team who provides instant technology support and remarks kinds of feedback from customers and makes efforts to cooperate with our engineers of R&D to develop latest automotive device.

Check out all OTC products available on OBD2TOOL.

4.XTOOL Scanner


Check out all OTC products available on OBD2TOOL.

Langren is committed to becoming a world-class provider of automotive integrated service platform based on automotive electronic control systems by developing, manufacturing and selling smart car diagnostic equipment, vehicle networking terminal products and solutions, and IoT smart hardware and solutions. And China’s leading provider of IoT solutions.



OTC is another big player in the automotive diagnostics sector. They produce not only professional level electronic diagnostic equipment for automobiles, but also automotive fuel maintenance equipment plus a range of tools for servicing their equipment and vehicles. All of this is done at their multiple facilities. In the end of 2012, they were acquired by Bosch.

Check out all OTC products available on OBD2TOOL.

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