How Does OBD (On-Board Diagnostics) Function?

Here we are with another automobile technology article. As is the case with all our previous articles, we try to bring to you the technological content in an easy-to-understand way. The aim is to make you gain some knowledge, considering that you are also an automobile enthusiast and are curious about all the techniques related to your cars. But without being too much technical, we try to make you aware of how these technologies work and their advantages and disadvantages. This time around, we have brought probably the most important aspect of the electronics of a vehicle. This article will discuss, in detail, the history, function, purpose of OBD systems in a car. So, let us dive straight into it.

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Bosch OBD Reader

OBD – Purpose

The purpose of the OBD systems keeps updating with time. On-Board Diagnostics, as the name suggests, is used for vehicle diagnostics. It is used to monitor various parameters inside a car’s engine. Being an electronic component, it communicates with all the other electronic components of the vehicle. This includes gathering data from all the sensors and sending the error signals to the ECU (Engine Control Unit) of the vehicle. The ECU is the brain of the computer which stores and corrects the data from all around the car. ECU will recognize the error signal and send the corrective signal to fix the problem.

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Now, there are a ton of errors that can be auto-corrected just by the action from the ECU. This includes correction of ignition timing to prevent knock inside the engine, signal the fuel injectors on the amount of fuel to be injected into the combustion cylinder of the engine, depending upon the throttle position. If, for example, the driver has pressed the accelerator pedal completely, that means that the driver wants to accelerate quicker and more power is required. Hence, more fuel needs to be injected into the cylinder to create more power. ECU makes sure that these changes are made within milliseconds. If for some reason, there is Knock inside the cylinder, the OBD will show the sign on the instrument cluster of the driver and the ECU will retard the ignition timing and the knock will go away.

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Similarly, if for some reason, the emission levels of the vehicle are heightened, OBD comes in handy. It will indicate that something like this is happening. If there is something to be done by the ECU itself, it will fix the issue, otherwise, the driver will know that he/she must take it to the service centre a get the problem checked out and fixed. In addition to this, one can keep an eye out for various parameters during the actual operation of the engine. The OBD port can be connected to the laptop and one can get the real-time reading of all the parameters to find out if any particular component of the vehicle is malfunctioning. Emission testing is the main purpose of the OBD because it gives real-time figures of the amount of NOx, CO and other exhaust components.

Other aspects of OBD are driver behaviour monitoring. Every driver has an individual driving style which can affect the fuel efficiency and other aspects of the vehicle. Especially for modern electric cars, driving behaviour determines the range that one will get from a single charge. Hence, keeping a tab on how one drives is of paramount importance.

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OBD – History

The history of the OBD goes back to 1969 when Volkswagen first introduced on-board with scanning capabilities. Ever since the trend and necessity of having computers on vehicles started. There were subsequent developments in this area by other car manufacturers as well. But the OBD that we know today, came about in 1988. The computers had more computing power at that time as compared to 1969. The first OBD is referred to as OBD – 1. The main features of this system were to control the emissions and monitor real-time parameters of the vehicle. The only problem with this system was that there was no standardization in terms of which letters donate what. If OBD found out some error, the way it would signal it was too different from other carmakers. Therefore, the error could mean different things for different types of cars. This made it hard for OBD to operate across the board for all the vehicles alike.

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In 1996, OBD-2 came into the picture remedying this issue. There were standard abbreviations that would be the same irrespective of the car company. This made the OBD adoption global and the best way to detect problems in the car. Once the problem is detected, it didn’t matter where you took the car to service, the OBD will show the same error. This was a brilliant milestone in OBD application after which the diagnostic aspects of the automobile industry were standardized and easy. The components used in the current cars include CAN buses for communication among various electronic components.

OBD – Application

There are various ways to read the parameters of the vehicle. Every car has an interface port where one can connect an electronic device to read the required parameters of the car.  These are the following.

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Code Readers

The very basic device used to read the parameters of the car is the hand scanner or reader. It has a small display, which reads out all the parameters and lets you know if there is a fault anywhere in the system. The display is not too detailed and the device is fairly inexpensive. That is why most of the private owners who want to read the parameters of their cars, use such devices.


The most widely used and effective method to read all the codes through the OBD system is via connecting it to a laptop. The official mechanics in the authorized dealerships across the board use laptops, where they get an overall view of all the parameters of the vehicle. It is also a faster way to see all the dimensions at once and even perform some simulations. A laptop can even correct if there is some fault by simply calibrating the system according to the need. Apart from a cable and software, not too many hardware components are needed to perform OBD on a vehicle.

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Apps on the smartphones

All modern cars come with Bluetooth connectivity as standard. This can be extended to the OBD system as well. By installing apps on smartphones to read the codes from an OBD system, one can easily know what is wrong with the vehicle. The smartphone can be connected to the app via Bluetooth and the real-time parameters of the vehicle can be read. These are some of the most common ways to get information from the ECU of your car.

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